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All Interview Questions — Topic-wise

1176 questions in learning order. Inside each topic the must-know questions come first, then the rest from easy to hard. Click a question to open its course's Q&A page with the short bullet-point answer.

★ Must know720 questions — asked in almost every interviewEasy to answerMedium to answerHard to answer

Fundamentals .NET Database Cloud & DevOps Frontend Automation Web3 Interview Questions

0. Fundamentals

1. .NET

C#48 questions · 23 must-know

What is the difference between a value type and a reference type?★ Must knowEasy to answer
What is the difference between string and StringBuilder?★ Must knowEasy to answer
Explain const vs readonly vs static readonly.★ Must knowEasy to answer
What are boxing and unboxing? Why avoid them?★ Must knowEasy to answer
What is the difference between == and .Equals()?★ Must knowEasy to answer
What are ref, out and in parameters?★ Must knowEasy to answer
Why should you use decimal instead of double for money?★ Must knowEasy to answer
What is the difference between Parse, TryParse and Convert?★ Must knowEasy to answer
What is the difference between Dictionary and Hashtable?★ Must knowEasy to answer
What is the difference between a multidimensional and a jagged array?★ Must knowEasy to answer
Explain IEnumerable, ICollection, IList and IQueryable.★ Must knowMedium to answer
What are delegates and events? How do they differ?★ Must knowMedium to answer
How does async/await work internally? Does it create a new thread?★ Must knowMedium to answer
What is the difference between Task.WhenAll and awaiting tasks one by one?★ Must knowMedium to answer
Why is async void dangerous?★ Must knowMedium to answer
What is IDisposable and the using statement? Dispose vs Finalize?★ Must knowMedium to answer
Explain garbage collection generations.★ Must knowMedium to answer
How do you create a custom exception, and when should you?★ Must knowMedium to answer
How do you make code thread-safe? Compare lock, Monitor, SemaphoreSlim, Interlocked and concurrent collections.★ Must knowHard to answer
What causes a deadlock with async code and how do you avoid it?★ Must knowHard to answer
A method builds a CSV of 200,000 rows using += on a string and takes minutes. What do you do?★ Must knowHard to answer
Your API's memory keeps growing until the pod restarts. How would you investigate?★ Must knowHard to answer
Two users update the same in-memory counter and some increments are lost. Why, and how do you fix it?★ Must knowHard to answer
What is the difference between var, dynamic and object?MediumEasy to answer
What is the difference between an array, ArrayList and List<T>?MediumEasy to answer
When do you use for, foreach, while and do-while?MediumEasy to answer
What is a namespace? Explain the two meanings of using.MediumEasy to answer
What are anonymous types?MediumEasy to answer
What is the difference between Stack and Queue?MediumEasy to answer
What are extension methods? Any limitations?MediumMedium to answer
What is the difference between struct and class?MediumMedium to answer
What are records and when do you use them?MediumMedium to answer
What are generics and what problem do they solve?MediumMedium to answer
What is the difference between throw and throw ex?MediumMedium to answer
What is the difference between Tuple and ValueTuple?MediumMedium to answer
What is the difference between Func, Action and Predicate?MediumMedium to answer
What is a multicast delegate?MediumMedium to answer
How do you read a very large file efficiently in C#?MediumMedium to answer
DateTime vs DateTimeOffset — which should you store?MediumMedium to answer
What is a [Flags] enum?MediumMedium to answer
What are Span<T> and Memory<T>?MediumHard to answer
What is the difference between Task and ValueTask?MediumHard to answer
A synchronous method calls GetDataAsync().Result and the app hangs under load. Explain and fix.MediumHard to answer
You need to call 500 external URLs as fast as possible without getting rate-limited. How?MediumHard to answer
You must count error lines in a 5 GB log file without running out of memory. How?MediumHard to answer
After deploying to the cloud, order times shown to users are 5.5 hours off. What went wrong?MediumHard to answer
What are covariance and contravariance?LowHard to answer
What are source generators and why are they replacing reflection?LowHard to answer

VB.NET16 questions · 8 must-know

What is the difference between VB.NET and C#?★ Must knowEasy to answer
What do Option Strict, Option Explicit and Option Infer do?★ Must knowEasy to answer
What is the difference between Sub and Function?★ Must knowEasy to answer
ByVal vs ByRef?★ Must knowEasy to answer
And vs AndAlso, Or vs OrElse?★ Must knowMedium to answer
How are events handled in VB.NET?★ Must knowMedium to answer
DirectCast vs CType vs TryCast?★ Must knowMedium to answer
You must maintain a large VB.NET Web Forms app and gradually move it to modern .NET. What is your plan?★ Must knowHard to answer
What are the VB.NET equivalents of static, this, null and abstract?MediumEasy to answer
Why does Dim arr(5) As Integer create 6 elements?MediumEasy to answer
What is the difference between On Error GoTo and Try/Catch?MediumMedium to answer
What is a Module in VB.NET?MediumMedium to answer
What are XML literals?MediumMedium to answer
Can a C# project and a VB.NET project be in the same solution?MediumHard to answer
Does VB.NET run on .NET 8/10?MediumHard to answer
After converting a VB function to C#, string results are off by one character. Why?MediumHard to answer

.NET Internals: CLR, Memory & GC19 questions · 12 must-know

What is the CLR and what does it do?★ Must knowEasy to answer
What are CTS and CLS?★ Must knowEasy to answer
What is IL (MSIL/CIL) and what does the JIT do?★ Must knowEasy to answer
What is the difference between .NET Framework, .NET Core and .NET 5+?★ Must knowEasy to answer
What is managed vs unmanaged code?★ Must knowEasy to answer
What is an assembly? What does it contain?★ Must knowEasy to answer
Explain how the garbage collector works. What are generations?★ Must knowMedium to answer
Dispose vs Finalize — what's the difference? What is the Dispose pattern?★ Must knowMedium to answer
Where are value types and reference types stored?★ Must knowMedium to answer
Workstation vs Server GC?★ Must knowMedium to answer
How do you find a memory leak in a production .NET application?★ Must knowHard to answer
An ASP.NET Core API's memory grows steadily until the container is OOM-killed every few hours. What do you do?★ Must knowHard to answer
What is the GAC and is it used in .NET Core?MediumMedium to answer
AppDomain vs AssemblyLoadContext?MediumMedium to answer
What is tiered compilation, ReadyToRun and Native AOT?MediumMedium to answer
How does async/await work internally?MediumMedium to answer
What is the Large Object Heap and why can it cause problems?MediumHard to answer
How does virtual method dispatch work in the CLR?MediumHard to answer
A console tool processes images and becomes slow with frequent gen-2 collections. Why?MediumHard to answer

OOP22 questions · 12 must-know

What are the four pillars of OOP? Explain each with an example.★ Must knowEasy to answer
What is the difference between a class and an object?★ Must knowEasy to answer
What is the difference between method overloading and method overriding?★ Must knowEasy to answer
What is the difference between an abstract class and an interface? When do you use which?★ Must knowEasy to answer
Does C# support multiple inheritance?★ Must knowEasy to answer
What are access modifiers? What are the defaults?★ Must knowEasy to answer
What is the difference between method overriding and method hiding (new)?★ Must knowMedium to answer
What is the difference between composition and inheritance? Why "favour composition"?★ Must knowMedium to answer
Explain association, aggregation and composition with examples.★ Must knowMedium to answer
Can you create an instance of an abstract class? Can an abstract class have a constructor?★ Must knowMedium to answer
You have Bird with a Fly() method and now need Penguin. How do you model it?★ Must knowHard to answer
A ReportGenerator class has methods for fetching data, formatting PDF and Excel, emailing and logging. It's 3,000 lines. How would you refactor it?★ Must knowHard to answer
What is a constructor? Can it be private or static?MediumEasy to answer
What is the sealed keyword?MediumEasy to answer
What are virtual methods? Why aren't methods virtual by default in C#?MediumMedium to answer
What is a static class? Static vs singleton?MediumMedium to answer
Why must you override GetHashCode when you override Equals?MediumMedium to answer
What is an interface default method (C# 8) and why was it added?MediumMedium to answer
What are cohesion and coupling? How do you measure them in practice?MediumHard to answer
Your team adds a new payment method every quarter, and each time someone edits a big switch statement in PaymentService. What design would you suggest?MediumHard to answer
An interviewer asks you to design classes for a parking lot. What would you show?MediumHard to answer
What are covariant return types (C# 9)?LowHard to answer

SOLID Principles15 questions · 8 must-know

What are the SOLID principles? Explain each briefly.★ Must knowEasy to answer
Give a real example of the Single Responsibility Principle.★ Must knowEasy to answer
How do you implement the Open/Closed Principle in C#?★ Must knowEasy to answer
Explain the Liskov Substitution Principle with the Rectangle–Square example.★ Must knowMedium to answer
What is the difference between Dependency Inversion, Dependency Injection and Inversion of Control?★ Must knowMedium to answer
What are the service lifetimes in ASP.NET Core DI and what is a captive dependency?★ Must knowMedium to answer
Your NotificationService sends email via SMTP using new SmtpClient() inside the method. The business now wants SMS and WhatsApp too, and tests keep sending real emails. What do you change?★ Must knowHard to answer
A code review shows if (shape is Circle) ... else if (shape is Square) ... in five places. What principle is violated and how do you fix it?★ Must knowHard to answer
Give an Interface Segregation example from .NET itself.MediumMedium to answer
Is it OK to violate SOLID sometimes?MediumMedium to answer
Which design patterns support which SOLID principles?MediumMedium to answer
How does Clean Architecture apply the Dependency Inversion Principle?MediumHard to answer
A background service crashes with "Cannot consume scoped service from singleton". Explain and fix.MediumHard to answer
How would you explain where you applied SOLID in your last project?MediumHard to answer
What is the Stable Dependencies / Stable Abstractions principle?LowHard to answer

Design Patterns21 questions · 13 must-know

What are design patterns? Name the three GoF categories.★ Must knowEasy to answer
How do you implement a thread-safe Singleton in C#?★ Must knowEasy to answer
What is the difference between Factory Method and Abstract Factory?★ Must knowEasy to answer
What is the Strategy pattern? Where have you used it?★ Must knowEasy to answer
What is the difference between Decorator and Adapter?★ Must knowMedium to answer
Explain the Repository and Unit of Work patterns. Do you need them with EF Core?★ Must knowMedium to answer
How is ASP.NET Core middleware an example of Chain of Responsibility?★ Must knowMedium to answer
What is the Observer pattern and how does C# support it?★ Must knowMedium to answer
Explain CQRS. When is it worth it?★ Must knowHard to answer
What is the Outbox pattern and why is it needed?★ Must knowHard to answer
How do Retry and Circuit Breaker work together?★ Must knowHard to answer
The product details page calls the DB for every request and is slow. You can't change the repository class. Which pattern helps?★ Must knowHard to answer
Your app must support three SMS vendors and switch between them by configuration or when one is down. Design it.★ Must knowHard to answer
What is the Facade pattern? Give a real example.MediumMedium to answer
What is the Builder pattern? Show .NET examples.MediumMedium to answer
What is the Mediator pattern and what does MediatR do?MediumMedium to answer
Template Method vs Strategy?MediumMedium to answer
What is the Saga pattern?MediumHard to answer
An expense approval needs Team Lead below ₹10,000, Manager up to ₹1,00,000, and Director above. Which pattern?MediumHard to answer
When an order is placed you must save it, publish OrderPlaced to Service Bus, and never lose the message even if the broker is down. How?MediumHard to answer
What is the Specification pattern?LowHard to answer

ADO.NET18 questions · 12 must-know

What is ADO.NET? Name its main objects.★ Must knowEasy to answer
What is the difference between connected and disconnected architecture?★ Must knowEasy to answer
What is the difference between ExecuteReader, ExecuteScalar and ExecuteNonQuery?★ Must knowEasy to answer
DataReader vs DataSet?★ Must knowEasy to answer
How do you prevent SQL injection in ADO.NET?★ Must knowEasy to answer
What is connection pooling? How do you troubleshoot pool exhaustion?★ Must knowMedium to answer
How do you implement a transaction in ADO.NET?★ Must knowMedium to answer
Why is AddWithValue considered bad practice?★ Must knowMedium to answer
How do you call a stored procedure with output parameters?★ Must knowMedium to answer
What is Dapper and how does it compare with EF Core and raw ADO.NET?★ Must knowMedium to answer
Under load the API logs "Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool." How do you fix it?★ Must knowHard to answer
You must import a 2-million-row CSV into SQL Server nightly. How would you do it in .NET?★ Must knowHard to answer
What is the using statement's role with SqlConnection?MediumEasy to answer
What is SqlBulkCopy and when do you use it?MediumMedium to answer
What is MARS?MediumMedium to answer
How do you handle transient errors (e.g. Azure SQL failovers) in ADO.NET?MediumHard to answer
How would you pass a list of 5,000 IDs to a SQL query efficiently?MediumHard to answer
A query is fast in SSMS but slow from the application. Why?MediumHard to answer

LINQ21 questions · 13 must-know

What is LINQ and what are its advantages?★ Must knowEasy to answer
What is deferred execution? Which operators execute immediately?★ Must knowEasy to answer
What is the difference between First, FirstOrDefault, Single and SingleOrDefault?★ Must knowEasy to answer
What is the difference between Select and SelectMany?★ Must knowEasy to answer
What is the difference between IEnumerable and IQueryable?★ Must knowEasy to answer
How do you perform a left outer join in LINQ?★ Must knowMedium to answer
Write a LINQ query to find the second highest salary.★ Must knowMedium to answer
How do you group data and get counts or sums per group?★ Must knowMedium to answer
What is the difference between Any() and Count() > 0?★ Must knowMedium to answer
What are expression trees and why does EF Core need them?★ Must knowHard to answer
What is the N+1 problem in LINQ/EF and how do you fix it?★ Must knowHard to answer
A report screen calls db.Orders.ToList().Where(o => o.CustomerId == id) and is slow with 2 million orders. What's wrong?★ Must knowHard to answer
Given a list of employees, write LINQ to return each department's highest-paid employee and the department's average salary.★ Must knowHard to answer
Query syntax vs method syntax — which is better?MediumEasy to answer
What is the difference between ToList(), ToArray(), ToDictionary() and ToLookup()?MediumMedium to answer
What is the difference between Union and Concat? Distinct with custom objects?MediumMedium to answer
What does let do in query syntax?MediumMedium to answer
Why might a LINQ query throw "could not be translated"?MediumHard to answer
When would you use PLINQ, and when not?MediumHard to answer
Find duplicate emails in a customer list and keep only the first record of each.MediumHard to answer
A method returns IEnumerable<Order> from a DB query, and two foreach loops over it hit the database twice. Why, and how do you fix it?MediumHard to answer

Entity Framework (EF6 & Core)23 questions · 14 must-know

What is Entity Framework Core and what are its advantages?★ Must knowEasy to answer
Code-first vs database-first?★ Must knowEasy to answer
What is DbContext? Is it thread-safe? What lifetime should it have?★ Must knowEasy to answer
What are migrations? What commands do you use?★ Must knowEasy to answer
What is the difference between eager, lazy and explicit loading?★ Must knowEasy to answer
What is change tracking? What is AsNoTracking?★ Must knowMedium to answer
Explain entity states in EF Core.★ Must knowMedium to answer
What is the N+1 problem and how do you avoid it in EF Core?★ Must knowMedium to answer
How does EF Core handle concurrency?★ Must knowMedium to answer
How do you configure relationships? Data annotations vs Fluent API?★ Must knowMedium to answer
How do you improve EF Core query performance?★ Must knowHard to answer
A page listing 50 orders takes 5 seconds and the log shows 51 SQL queries. Fix it.★ Must knowHard to answer
Two users edit the same product price at the same time and the later save silently overwrites the earlier one. How do you prevent lost updates?★ Must knowHard to answer
You need to delete 5 million log rows older than 90 days nightly without blocking the app. What do you do?★ Must knowHard to answer
What is the difference between Find and FirstOrDefault?MediumEasy to answer
What are global query filters? Give use cases.MediumMedium to answer
How do you execute raw SQL or stored procedures in EF Core?MediumMedium to answer
What are ExecuteUpdate and ExecuteDelete?MediumMedium to answer
What is the difference between DbContext and ObjectContext?MediumMedium to answer
What is the difference between Update() and attaching then setting properties?MediumHard to answer
EF Core vs EF6 — key differences?MediumHard to answer
Deploying a migration renamed a column and dropped production data. How do you prevent this?MediumHard to answer
A BackgroundService throws "A second operation was started on this context instance before a previous operation completed." Why?MediumHard to answer

Dapper15 questions · 8 must-know

What is Dapper and why use it?★ Must knowEasy to answer
Dapper vs Entity Framework Core?★ Must knowEasy to answer
How does Dapper prevent SQL injection?★ Must knowEasy to answer
Difference between Query, QueryFirst, QuerySingle and Execute?★ Must knowEasy to answer
How do you call a stored procedure with output parameters in Dapper?★ Must knowMedium to answer
What is multi-mapping and what does splitOn do?★ Must knowMedium to answer
How do you use transactions with Dapper?★ Must knowMedium to answer
A Dapper search endpoint is slow even though the same SQL is fast in SSMS. What could cause it?★ Must knowHard to answer
How do you insert thousands of rows efficiently?MediumMedium to answer
What is buffered vs unbuffered querying in Dapper?MediumMedium to answer
How does Dapper map columns to properties and how do you handle mismatched names?MediumMedium to answer
How does Dapper achieve its performance?MediumHard to answer
How do you manage connections with Dapper in ASP.NET Core?MediumHard to answer
Your team builds SQL with string interpolation for filters in Dapper. What problems does this cause and how do you fix it?MediumHard to answer
How would you migrate a large ADO.NET DataReader-based data layer to Dapper?MediumHard to answer

ASP.NET Web Forms17 questions · 11 must-know

Explain the ASP.NET Web Forms page life cycle.★ Must knowEasy to answer
What is ViewState? Pros and cons?★ Must knowEasy to answer
What is PostBack and IsPostBack?★ Must knowEasy to answer
What state management options exist in ASP.NET?★ Must knowEasy to answer
Response.Redirect vs Server.Transfer?★ Must knowEasy to answer
What are the Session state modes? Which would you use in a web farm?★ Must knowMedium to answer
User control vs custom control?★ Must knowMedium to answer
What are master pages and how do content pages use them?★ Must knowMedium to answer
What is the role of Global.asax and web.config?★ Must knowMedium to answer
A Web Forms page with a big GridView is very slow to post back. How do you fix it?★ Must knowHard to answer
You must add a new feature to a legacy Web Forms app while the company plans to move to ASP.NET Core. How do you build it?★ Must knowHard to answer
HTTP module vs HTTP handler?MediumMedium to answer
What does an UpdatePanel actually do?MediumMedium to answer
How do you handle errors globally in Web Forms?MediumMedium to answer
Why does a dynamically added control lose its value or events after postback?MediumHard to answer
What is the difference between a Web Site project and a Web Application project?MediumHard to answer
Users randomly lose their session (shopping cart) in production. What could cause it?MediumHard to answer

ASP.NET MVC 516 questions · 10 must-know

What is MVC? Explain Model, View and Controller.★ Must knowEasy to answer
Explain the ASP.NET MVC 5 request life cycle.★ Must knowEasy to answer
Describe the MVC 5 folder structure.★ Must knowEasy to answer
ViewData vs ViewBag vs TempData?★ Must knowEasy to answer
What types of ActionResult are there?★ Must knowEasy to answer
What are filters in MVC? Name the types and their order.★ Must knowMedium to answer
Conventional routing vs attribute routing?★ Must knowMedium to answer
How does model binding and validation work?★ Must knowMedium to answer
Partial view vs child action (vs view component in Core)?★ Must knowMedium to answer
You must migrate a large MVC 5 app to ASP.NET Core without stopping feature work. How?★ Must knowHard to answer
How do you implement dependency injection in MVC 5?MediumMedium to answer
What is the Post-Redirect-Get pattern and why use it?MediumMedium to answer
How do you prevent CSRF and XSS in MVC 5?MediumMedium to answer
How do you handle errors globally in MVC 5?MediumHard to answer
What are Areas and when do you use them?MediumHard to answer
An action returns stale data because of [OutputCache]. How do you fix it while keeping performance?MediumHard to answer

Modern .NET: Host, Config, DI17 questions · 10 must-know

What is the difference between .NET Framework, .NET Core and .NET 5/6/8/10?★ Must knowEasy to answer
What is the CLR and what does it do?★ Must knowEasy to answer
What is JIT compilation? What are ReadyToRun and Native AOT?★ Must knowEasy to answer
What are LTS and STS releases?★ Must knowEasy to answer
Explain the order of configuration sources in ASP.NET Core.★ Must knowMedium to answer
What is the difference between IOptions, IOptionsSnapshot and IOptionsMonitor?★ Must knowMedium to answer
What is a BackgroundService / IHostedService?★ Must knowMedium to answer
How does the .NET garbage collector work? Workstation vs Server GC?★ Must knowHard to answer
Your ASP.NET Core API on .NET 8 must keep getting security patches after November 2026. What do you do and when?★ Must knowHard to answer
An API's CPU is fine but requests queue up and latency spikes under load. Thread count keeps growing. What's happening?★ Must knowHard to answer
What is an assembly? What is the GAC?MediumEasy to answer
What is .NET Standard? Do I still need it?MediumEasy to answer
What is Kestrel? Do you still need IIS?MediumMedium to answer
Framework-dependent vs self-contained deployment?MediumMedium to answer
What are the limitations of Native AOT?MediumHard to answer
How would you migrate a large ASP.NET MVC 5 app on .NET Framework 4.8 to .NET 10?MediumHard to answer
Configuration works locally but in Azure App Service the app uses the wrong connection string. How do you debug it?MediumHard to answer

ASP.NET Core MVC23 questions · 14 must-know

What is MVC? Explain the role of each component.★ Must knowEasy to answer
Explain the ASP.NET Core MVC request lifecycle.★ Must knowEasy to answer
What is the difference between ViewData, ViewBag and TempData?★ Must knowEasy to answer
What is the difference between conventional and attribute routing?★ Must knowEasy to answer
What is model binding?★ Must knowEasy to answer
How does validation work in ASP.NET Core MVC?★ Must knowEasy to answer
Partial view vs view component — when do you use which?★ Must knowMedium to answer
What are filters? List the types and their execution order.★ Must knowMedium to answer
What is the difference between middleware and filters?★ Must knowMedium to answer
What are tag helpers? How are they better than HTML helpers?★ Must knowMedium to answer
How do you prevent CSRF attacks in ASP.NET Core MVC?★ Must knowMedium to answer
How does authentication differ between an MVC app and a Web API?★ Must knowHard to answer
Users double-click "Place Order" and two orders are created. How do you fix it?★ Must knowHard to answer
A product page shows another customer's order when the URL ID is changed. What is the bug and the fix?★ Must knowHard to answer
What are _Layout, _ViewStart and _ViewImports?MediumEasy to answer
What is the difference between RedirectToAction, Redirect and LocalRedirect?MediumMedium to answer
What is Post-Redirect-Get and why is it used?MediumMedium to answer
What is an Area in MVC?MediumMedium to answer
How do you handle errors globally in MVC?MediumMedium to answer
How would you implement resource-based authorisation (e.g. only the owner can edit a document)?MediumHard to answer
How do you unit-test an MVC controller?MediumHard to answer
Your MVC home page takes 4 seconds. Profiling shows 120 SQL queries per request. What do you do?MediumHard to answer
After deploying, users see old CSS/JS from browser cache. How do you prevent this?MediumHard to answer

ASP.NET Core Web API25 questions · 17 must-know

What is REST? What are its constraints?★ Must knowEasy to answer
What is the difference between PUT, POST and PATCH?★ Must knowEasy to answer
What is the difference between 401 and 403?★ Must knowEasy to answer
What does the [ApiController] attribute do?★ Must knowEasy to answer
What is middleware? How do you write custom middleware?★ Must knowEasy to answer
What is the difference between IActionResult and ActionResult<T>?★ Must knowEasy to answer
Controllers vs Minimal APIs — which do you choose?★ Must knowMedium to answer
How does JWT authentication work in ASP.NET Core?★ Must knowMedium to answer
What is CORS and why do you get CORS errors?★ Must knowMedium to answer
Why should you use IHttpClientFactory?★ Must knowMedium to answer
How do you handle exceptions globally in a Web API?★ Must knowMedium to answer
How do you version an API?★ Must knowMedium to answer
How do you make a POST endpoint idempotent (e.g. payments)?★ Must knowHard to answer
How would you secure a public Web API end to end?★ Must knowHard to answer
Your API returns 200 OK with { "success": false, "error": "Not found" } for everything. How would you improve it?★ Must knowHard to answer
An endpoint that lists orders is slow (3 s) for a customer with 50,000 orders. What do you do?★ Must knowHard to answer
A downstream payment API is slow and occasionally down, and your API threads pile up. How do you protect your service?★ Must knowHard to answer
What is Swagger/OpenAPI and how do you add it to an ASP.NET Core API?MediumEasy to answer
What is content negotiation?MediumMedium to answer
How do you implement pagination? Offset vs keyset?MediumMedium to answer
What are the rate-limiting algorithms in ASP.NET Core?MediumMedium to answer
gRPC vs REST — when do you use gRPC?MediumHard to answer
How do you test a Web API?MediumHard to answer
Mobile clients on an old app version break when you rename a JSON field. How do you avoid this in future?MediumHard to answer
After scaling the API to 3 instances, users randomly get logged out and in-memory cache data differs. Why?MediumHard to answer

Exception Handling & Custom Errors16 questions · 10 must-know

What is the difference between throw and throw ex?★ Must knowEasy to answer
What are best practices for exception handling in .NET?★ Must knowEasy to answer
What does finally do? When doesn't it run?★ Must knowEasy to answer
How do you create a custom exception?★ Must knowEasy to answer
How do you implement global exception handling in ASP.NET Core?★ Must knowMedium to answer
Middleware vs exception filter for handling exceptions — which and why?★ Must knowMedium to answer
How are errors handled in ASP.NET MVC 5 and Web Forms?★ Must knowMedium to answer
Exceptions or Result objects — when to use which?★ Must knowMedium to answer
Users see a yellow error page with SQL details in production. What do you change?★ Must knowHard to answer
An API returns 500 for "customer not found" and "invalid quantity". How do you improve it?★ Must knowHard to answer
How do exceptions behave with async/await and Task.WhenAll?MediumMedium to answer
What is ProblemDetails?MediumMedium to answer
How do you handle a unique-key violation from SQL Server?MediumMedium to answer
What happens to an unhandled exception in a background thread or BackgroundService?MediumHard to answer
Why should you not catch System.Exception everywhere?MediumHard to answer
Intermittent "deadlock victim" errors appear under load. How do you handle them in code?MediumHard to answer

Logging & Custom Logging16 questions · 7 must-know

What are the log levels in .NET and when do you use each?★ Must knowEasy to answer
What is structured logging and why is it better than string logs?★ Must knowEasy to answer
How does logging work in ASP.NET Core?★ Must knowEasy to answer
Serilog vs NLog vs log4net vs built-in ILogger?★ Must knowMedium to answer
How do you correlate logs across multiple services?★ Must knowMedium to answer
How would you write a custom logger in .NET?★ Must knowMedium to answer
Production has an intermittent bug you can't reproduce. How do you use logging to find it?★ Must knowHard to answer
What should never be logged?MediumEasy to answer
What is the difference between Console.WriteLine/Debug.WriteLine and a logging framework?MediumEasy to answer
What are logging scopes?MediumMedium to answer
What is the difference between audit logging and application logging?MediumMedium to answer
How do you change log levels in production without redeploying?MediumMedium to answer
How do you make logging fast and avoid performance problems?MediumHard to answer
How did you log errors in .NET Framework Web Forms/MVC apps?MediumHard to answer
Logging costs on the cloud are exploding. What do you change?MediumHard to answer
The app writes logs to a database, and when the database is slow, requests become slow too. Fix it.MediumHard to answer

Custom Controls & Components16 questions · 6 must-know

What is the difference between a user control and a custom control in ASP.NET?★ Must knowEasy to answer
What is a custom HTML helper in MVC and how do you create one?★ Must knowEasy to answer
What are tag helpers? How do they differ from HTML helpers?★ Must knowEasy to answer
View component vs partial view?★ Must knowMedium to answer
How do you create a reusable Blazor component? How does a child notify a parent?★ Must knowMedium to answer
Twenty MVC pages repeat the same "price with discount badge" markup with slight differences. What do you build?★ Must knowHard to answer
What is the difference between Control, WebControl and CompositeControl in Web Forms?MediumEasy to answer
How do you keep a custom Web Forms control's property value across postbacks?MediumMedium to answer
What is a Razor Class Library?MediumMedium to answer
How do you make a Blazor component support two-way binding with @bind-Value?MediumMedium to answer
What are display and editor templates in MVC?MediumMedium to answer
How do you share UI components across several ASP.NET Core applications?MediumMedium to answer
What are dependency properties in WPF and why do custom controls use them?MediumHard to answer
How do you test UI components?MediumHard to answer
A dynamically created custom control in Web Forms loses its value and its Click event doesn't fire. Why?MediumHard to answer
A Blazor grid component with 5,000 rows makes the page slow. How do you improve it?MediumHard to answer

Project Architecture & Folders15 questions · 7 must-know

Explain 3-tier (N-layer) architecture.★ Must knowEasy to answer
What is Clean Architecture? What is the dependency rule?★ Must knowEasy to answer
How do you structure a typical ASP.NET Core Web API solution?★ Must knowEasy to answer
Onion vs Clean vs Hexagonal architecture?★ Must knowMedium to answer
Vertical Slice vs layered architecture?★ Must knowMedium to answer
Where do you put the repository interfaces and why?★ Must knowMedium to answer
You join a project where controllers contain SQL, business rules and email sending. How do you restructure it safely?★ Must knowHard to answer
What is the composition root?MediumEasy to answer
What is a modular monolith?MediumMedium to answer
Layer vs tier?MediumMedium to answer
What is CQRS? Do you need MediatR for it?MediumMedium to answer
How do you prevent architecture erosion over time?MediumHard to answer
What are aggregates and why do they matter for structure?MediumHard to answer
A small internal tool (5 screens) is being built with 8 projects in Clean Architecture. Is that right?MediumHard to answer
How would you organise a solution with an ASP.NET Core API, an Angular front end and background workers?MediumHard to answer

Clean Code & Unit Testing18 questions · 10 must-know

What is clean code? What practices do you follow?★ Must knowEasy to answer
What is unit testing? What makes a good unit test?★ Must knowEasy to answer
What is the difference between [Fact] and [Theory] in xUnit?★ Must knowEasy to answer
What is mocking? Mock vs stub vs fake?★ Must knowMedium to answer
How do you unit-test code that uses DateTime.Now, HttpClient or a database?★ Must knowMedium to answer
What is TDD? Have you used it?★ Must knowMedium to answer
What is the test pyramid?★ Must knowMedium to answer
What do you check in a code review?★ Must knowMedium to answer
You join a team with a 10-year-old codebase, no tests and frequent production bugs. What's your plan?★ Must knowHard to answer
A reviewer rejects your PR saying the method is too long and untestable. How do you respond and fix it?★ Must knowHard to answer
What are xUnit, NUnit and MSTest? Differences?MediumEasy to answer
What are code smells? Name five and their fixes.MediumMedium to answer
Merge vs rebase? What is a squash merge?MediumMedium to answer
Trunk-based development vs GitFlow?MediumMedium to answer
What is mutation testing?MediumHard to answer
How do you prevent SQL injection and IDOR in a .NET API?MediumHard to answer
A test passes locally but fails randomly in CI. What could cause it?MediumHard to answer
Production logs show Object reference not set to an instance of an object with no context. How do you make this debuggable next time?MediumHard to answer

Microservices & System Design20 questions · 14 must-know

What are microservices? What are their advantages and disadvantages?★ Must knowEasy to answer
Monolith vs microservices — which would you choose for a new project?★ Must knowEasy to answer
How do microservices communicate?★ Must knowEasy to answer
What is an API gateway and why use one?★ Must knowEasy to answer
What is "database per service" and how do you query data across services?★ Must knowMedium to answer
Explain the saga pattern. Choreography vs orchestration?★ Must knowMedium to answer
What is the outbox pattern and what problem does it solve?★ Must knowMedium to answer
How do you make a service resilient to failures of its dependencies?★ Must knowMedium to answer
What is idempotency and why is it important in distributed systems?★ Must knowMedium to answer
How do you handle data consistency without distributed transactions?★ Must knowHard to answer
Explain CQRS. When is it worth it?★ Must knowHard to answer
Design a URL shortener.★ Must knowHard to answer
An order service calls payment, which calls a slow fraud check; under load the whole site times out. What do you change?★ Must knowHard to answer
Customers are charged twice when the client retries a payment request. Fix it.★ Must knowHard to answer
REST vs gRPC — when would you choose gRPC?MediumMedium to answer
How do you implement distributed tracing in .NET?MediumMedium to answer
How do you version APIs and events without breaking consumers?MediumHard to answer
How do you scale a .NET service horizontally?MediumHard to answer
You must split a large .NET monolith into services. How do you start?MediumHard to answer
A message consumer keeps failing on one bad message and blocks the queue. What do you do?MediumHard to answer

2. Database, ETL & BI

SQL Server & T-SQL30 questions · 21 must-know

What is the difference between DELETE, TRUNCATE and DROP?★ Must knowEasy to answer
What are the different types of joins?★ Must knowEasy to answer
What is the difference between WHERE and HAVING?★ Must knowEasy to answer
What is a primary key vs a unique key vs a foreign key?★ Must knowEasy to answer
What is normalisation? Explain 1NF, 2NF and 3NF.★ Must knowEasy to answer
Clustered vs non-clustered index?★ Must knowEasy to answer
Write a query to find the second (or Nth) highest salary.★ Must knowEasy to answer
How do you find and delete duplicate rows?★ Must knowEasy to answer
What are the ACID properties of a transaction?★ Must knowEasy to answer
Explain ROW_NUMBER, RANK and DENSE_RANK.★ Must knowMedium to answer
What is a CTE? When would you use a recursive CTE?★ Must knowMedium to answer
Stored procedure vs function?★ Must knowMedium to answer
What are the transaction isolation levels in SQL Server?★ Must knowMedium to answer
What is a deadlock and how do you handle it?★ Must knowMedium to answer
Temp table vs table variable vs CTE?★ Must knowMedium to answer
What makes a query non-SARGable? Give examples.★ Must knowMedium to answer
What is parameter sniffing and how do you fix it?★ Must knowHard to answer
How do you approach tuning a slow query?★ Must knowHard to answer
A report query that used to take 2 seconds now takes 2 minutes. Nothing in the code changed. What do you check?★ Must knowHard to answer
Write a query to get each department's top 3 earners.★ Must knowHard to answer
Users report the Orders screen freezes at month-end when the finance job runs. How do you investigate and fix?★ Must knowHard to answer
What is the difference between UNION and UNION ALL?MediumEasy to answer
What is the difference between CHAR, VARCHAR, NCHAR and NVARCHAR?MediumEasy to answer
What is the difference between ISNULL and COALESCE?MediumMedium to answer
What are the magic tables in triggers?MediumMedium to answer
What does NOLOCK do and why is it dangerous?MediumHard to answer
Explain the backup types and recovery models.MediumHard to answer
How would you design tables for an e-commerce order system?MediumHard to answer
You must load 50 million rows into a table that is queried 24/7. How do you avoid downtime?MediumHard to answer
What is lock escalation?LowHard to answer

SQL Server Internals18 questions · 12 must-know

What is the difference between a clustered and a nonclustered index?★ Must knowEasy to answer
What is a page and an extent in SQL Server?★ Must knowEasy to answer
What are the transaction isolation levels in SQL Server?★ Must knowEasy to answer
What is an execution plan and how do you read it?★ Must knowEasy to answer
How does SQL Server process a query internally?★ Must knowMedium to answer
What are statistics and why do they matter?★ Must knowMedium to answer
What is parameter sniffing? How do you fix it?★ Must knowMedium to answer
What is write-ahead logging and how does SQL Server recover after a crash?★ Must knowMedium to answer
What causes blocking and how do you troubleshoot it?★ Must knowMedium to answer
Why can NOLOCK be dangerous?★ Must knowHard to answer
A query was fast yesterday and is slow today with no code change. How do you investigate?★ Must knowHard to answer
Users get "Transaction was deadlocked … chosen as the deadlock victim". What do you do?★ Must knowHard to answer
What is a key lookup and how do you remove it?MediumMedium to answer
What is the buffer pool?MediumMedium to answer
Latch vs lock?MediumMedium to answer
When would you use a columnstore index?MediumHard to answer
Why does the transaction log keep growing?MediumHard to answer
An insert-heavy table with an IDENTITY clustered key shows PAGELATCH_EX waits under load. Why and how to fix?MediumHard to answer

ETL & Data Warehouse19 questions · 11 must-know

What is ETL? Explain each step.★ Must knowEasy to answer
What is the difference between ETL and ELT?★ Must knowEasy to answer
What is a data warehouse? How is it different from an OLTP database?★ Must knowEasy to answer
What are fact and dimension tables?★ Must knowEasy to answer
What is the difference between a star schema and a snowflake schema?★ Must knowEasy to answer
Explain Slowly Changing Dimensions Types 1, 2 and 3.★ Must knowMedium to answer
What is a surrogate key and why use it in a warehouse?★ Must knowMedium to answer
How do you implement an incremental load?★ Must knowMedium to answer
How do you handle errors and bad data in ETL?★ Must knowMedium to answer
The nightly ETL that used to take 1 hour now takes 5 hours and misses the SLA. How do you troubleshoot?★ Must knowHard to answer
Business reports show sales totals 3% higher than the ERP. How do you find the cause?★ Must knowHard to answer
What is a staging area and why use it?MediumEasy to answer
What is the grain of a fact table and why is it important?MediumMedium to answer
What are additive, semi-additive and non-additive measures?MediumMedium to answer
What is CDC (Change Data Capture)?MediumMedium to answer
Inmon vs Kimball — which approach would you choose?MediumHard to answer
What is a late-arriving dimension (early-arriving fact) and how do you handle it?MediumHard to answer
Design an ETL for daily sales from 50 store databases into a central warehouse.MediumHard to answer
How do you test an ETL pipeline?MediumHard to answer

SSIS21 questions · 13 must-know

What is SSIS and what is it used for?★ Must knowEasy to answer
What is the difference between Control Flow and Data Flow?★ Must knowEasy to answer
What are the different types of containers?★ Must knowEasy to answer
What is a precedence constraint?★ Must knowEasy to answer
What is the difference between variables and parameters?★ Must knowEasy to answer
What are synchronous and asynchronous transformations? Give examples of blocking transformations.★ Must knowMedium to answer
Explain the Lookup transformation cache modes.★ Must knowMedium to answer
How do you handle errors in SSIS?★ Must knowMedium to answer
How do you implement an incremental load in SSIS?★ Must knowMedium to answer
What is the difference between the project and package deployment models?★ Must knowMedium to answer
How do you improve the performance of a slow SSIS package?★ Must knowHard to answer
A package that loads 10 million rows nightly suddenly fails with a truncation error on one column. How do you handle it?★ Must knowHard to answer
You need to process every CSV file that lands in a folder, archive successfully processed files and move bad files to an error folder. Design it.★ Must knowHard to answer
What is a connection manager?MediumEasy to answer
What are checkpoints in SSIS?MediumMedium to answer
Merge vs Merge Join vs Union All?MediumMedium to answer
How do you deploy and schedule SSIS packages?MediumMedium to answer
What are the SSISDB logging levels?MediumHard to answer
How do you run SSIS in the cloud?MediumHard to answer
The same package must run against DEV, QA and PROD servers with different connection strings and file paths. How do you configure it?MediumHard to answer
Your Lookup returns "No Match" for values that clearly exist in the reference table. Why?MediumHard to answer

SSRS18 questions · 10 must-know

What is SSRS and what are its main components?★ Must knowEasy to answer
What is the difference between a table, matrix and list?★ Must knowEasy to answer
What is the difference between a shared and an embedded data source?★ Must knowEasy to answer
What are report parameters? How do you create cascading parameters?★ Must knowEasy to answer
What is the difference between drill-down and drill-through reports?★ Must knowMedium to answer
How do you pass a multi-value parameter to a stored procedure?★ Must knowMedium to answer
What are subscriptions? Standard vs data-driven?★ Must knowMedium to answer
How do you improve SSRS report performance?★ Must knowMedium to answer
A report takes 3 minutes to open. ExecutionLog3 shows TimeDataRetrieval 170 seconds. What do you do?★ Must knowHard to answer
Managers want each region's sales report emailed to them every Monday, but only their region. How?★ Must knowHard to answer
What rendering/export formats does SSRS support?MediumEasy to answer
What is the difference between caching and snapshots?MediumMedium to answer
How do you show "Page X of Y" and alternating row colours?MediumMedium to answer
How do you implement row-level security in SSRS?MediumMedium to answer
What is the Lookup function? How is it different from a subreport?MediumHard to answer
What happened to SSRS after SQL Server 2022?MediumHard to answer
A report looks fine in the browser but the PDF export has blank pages. Why?MediumHard to answer
Subscriptions suddenly stopped sending emails. How do you troubleshoot?MediumHard to answer

3. Cloud & DevOps

IIS & Hosting .NET Apps16 questions · 10 must-know

What is IIS and what can it host?★ Must knowEasy to answer
What is an application pool and why is it used?★ Must knowEasy to answer
What is w3wp.exe?★ Must knowEasy to answer
How do you deploy an ASP.NET Core app to IIS?★ Must knowEasy to answer
In-process vs out-of-process hosting for ASP.NET Core in IIS?★ Must knowMedium to answer
What is app pool recycling and what are its effects?★ Must knowMedium to answer
What is ApplicationPoolIdentity and how do you give it permissions?★ Must knowMedium to answer
How do you troubleshoot a 500.30 / 502.5 error with ASP.NET Core on IIS?★ Must knowMedium to answer
After deployment the site returns 503 Service Unavailable. What do you check?★ Must knowHard to answer
An intranet ASP.NET app on IIS must use Windows login and query SQL Server as the user. How do you configure it?★ Must knowHard to answer
What is the difference between a site, an application and a virtual directory?MediumEasy to answer
What does HTTP.sys do?MediumMedium to answer
URL Rewrite vs Redirect? How do you host an Angular/React SPA on IIS?MediumMedium to answer
How do you set up a web farm with IIS?MediumHard to answer
What is a web garden and when should you avoid it?MediumHard to answer
The first request every morning takes 30 seconds. How do you fix it?MediumHard to answer

Git & GitHub19 questions · 11 must-know

What is Git and how is it different from SVN/TFVC?★ Must knowEasy to answer
What is the difference between git fetch and git pull?★ Must knowEasy to answer
What is the staging area?★ Must knowEasy to answer
How do you resolve a merge conflict?★ Must knowEasy to answer
Merge vs rebase — differences and when to use each?★ Must knowMedium to answer
git reset vs git revert?★ Must knowMedium to answer
Which branching strategy have you used? Explain it.★ Must knowMedium to answer
What is a pull request and what do you check in a code review?★ Must knowMedium to answer
You committed a password and pushed it to GitHub. What do you do?★ Must knowHard to answer
You made three commits on main by mistake instead of a feature branch (not pushed). Fix it.★ Must knowHard to answer
A bad commit is already deployed from main. How do you undo it without rewriting history?★ Must knowHard to answer
What does .gitignore do? A file is still tracked after adding it to .gitignore — why?MediumEasy to answer
What is git stash?MediumMedium to answer
What is cherry-pick and when would you use it?MediumMedium to answer
What is a detached HEAD?MediumHard to answer
How does git bisect help find a bug?MediumHard to answer
How does Git store data internally?MediumHard to answer
Your feature branch is two weeks behind main and has many conflicts. How do you bring it up to date?MediumHard to answer
git push is rejected with "non-fast-forward". What does it mean?MediumHard to answer

Docker18 questions · 11 must-know

What is Docker and why use it?★ Must knowEasy to answer
What is the difference between a container and a virtual machine?★ Must knowEasy to answer
What is the difference between an image and a container?★ Must knowEasy to answer
Explain the common Dockerfile instructions. CMD vs ENTRYPOINT? COPY vs ADD?★ Must knowEasy to answer
What is a multi-stage build and why use it?★ Must knowEasy to answer
What is Docker Compose and when would you use it?★ Must knowMedium to answer
How do containers in Docker communicate with each other?★ Must knowMedium to answer
How do you reduce Docker image size?★ Must knowMedium to answer
How do you handle secrets with Docker?★ Must knowMedium to answer
Your ASP.NET Core container starts but you get "connection refused" on http://localhost:8080. What do you check?★ Must knowHard to answer
The image is 2.1 GB and deploys slowly. How do you shrink it?★ Must knowHard to answer
What is the difference between a volume and a bind mount?MediumEasy to answer
What is layer caching? How do you write a cache-friendly Dockerfile?MediumMedium to answer
What do container exit codes 0, 1, 137 and 143 mean?MediumMedium to answer
How does Docker isolate containers under the hood?MediumHard to answer
Why did Kubernetes "remove Docker" and does it matter?MediumHard to answer
A container keeps restarting with exit code 137. What's happening?MediumHard to answer
Developers need SQL Server, Redis and RabbitMQ locally to run the API. How do you make onboarding one command?MediumHard to answer

Kubernetes21 questions · 14 must-know

What is Kubernetes and what problems does it solve?★ Must knowEasy to answer
Explain the Kubernetes architecture.★ Must knowEasy to answer
What is a Pod? Why not run containers directly?★ Must knowEasy to answer
What is the difference between a Deployment, a ReplicaSet and a StatefulSet?★ Must knowEasy to answer
What are the Service types in Kubernetes?★ Must knowEasy to answer
What is the difference between ConfigMap and Secret?★ Must knowMedium to answer
Explain liveness, readiness and startup probes.★ Must knowMedium to answer
What is the difference between resource requests and limits? What happens when exceeded?★ Must knowMedium to answer
How does a rolling update work? How do you roll back?★ Must knowMedium to answer
What is an Ingress? How is it different from a LoadBalancer Service?★ Must knowMedium to answer
How do you secure a Kubernetes cluster?★ Must knowHard to answer
A pod is stuck in CrashLoopBackOff. How do you troubleshoot?★ Must knowHard to answer
After deploying a new version, users get errors for a few seconds on every release. How do you get true zero-downtime deployments?★ Must knowHard to answer
Pods are Pending with "0/3 nodes are available: insufficient memory". What do you do?★ Must knowHard to answer
What is a namespace?MediumEasy to answer
What is Helm?MediumMedium to answer
How does autoscaling work in Kubernetes?MediumMedium to answer
What is a sidecar container? Give examples.MediumHard to answer
What happens when you run kubectl apply -f deployment.yaml?MediumHard to answer
The API in AKS must read secrets from Azure Key Vault without storing any credentials. How?MediumHard to answer
Should you run SQL Server inside Kubernetes for production?MediumHard to answer

Azure DevOps CI/CD18 questions · 11 must-know

What is DevOps? What are CI and CD?★ Must knowEasy to answer
What services does Azure DevOps provide?★ Must knowEasy to answer
Explain the structure of a YAML pipeline.★ Must knowEasy to answer
YAML pipelines vs classic pipelines?★ Must knowEasy to answer
What are branch policies and why use them?★ Must knowMedium to answer
How do you manage secrets in Azure Pipelines?★ Must knowMedium to answer
What are environments, approvals and checks?★ Must knowMedium to answer
What is the difference between ${{ }}, $[ ] and $( )?★ Must knowMedium to answer
How would you design a CI/CD pipeline for a .NET microservice deployed to AKS?★ Must knowHard to answer
The build is green but production broke after deployment. How do you prevent this next time?★ Must knowHard to answer
Pipelines take 40 minutes and developers are frustrated. How do you speed them up?★ Must knowHard to answer
What is an agent? Microsoft-hosted vs self-hosted?MediumEasy to answer
How do you reuse pipeline logic across projects?MediumMedium to answer
What branching strategy would you recommend and why?MediumMedium to answer
How do you deploy database changes in a pipeline?MediumMedium to answer
What are DORA metrics?MediumHard to answer
A teammate committed a production connection string to the repo. What do you do?MediumHard to answer
How do you achieve zero-downtime deployments to Azure App Service from a pipeline?MediumHard to answer

Microsoft Azure20 questions · 13 must-know

What are IaaS, PaaS and SaaS? Give Azure examples.★ Must knowEasy to answer
Explain the Azure resource hierarchy.★ Must knowEasy to answer
What is a managed identity and why use it?★ Must knowEasy to answer
What are deployment slots in App Service?★ Must knowEasy to answer
Service Bus vs Event Grid vs Event Hubs — when do you use each?★ Must knowMedium to answer
What are Azure Functions triggers and bindings? Which hosting plan would you choose?★ Must knowMedium to answer
What are Durable Functions?★ Must knowMedium to answer
How do you choose between Azure SQL Database and Cosmos DB?★ Must knowMedium to answer
What are Cosmos DB consistency levels?★ Must knowMedium to answer
How would you design a highly available, globally distributed web app on Azure?★ Must knowHard to answer
Your App Service API slows down every day at 9 AM and CPU hits 100%. What do you do?★ Must knowHard to answer
An order API must notify inventory, billing and email services reliably when an order is placed. Design it on Azure.★ Must knowHard to answer
A developer's connection string with the SQL admin password was found in appsettings.json in the repo. How do you fix the design?★ Must knowHard to answer
What are availability zones and region pairs?MediumEasy to answer
What is the difference between blob access tiers?MediumMedium to answer
How do you secure secrets for an app hosted in Azure?MediumMedium to answer
What is Azure API Management used for?MediumMedium to answer
How do you reduce Azure costs for an application?MediumHard to answer
Users in Europe complain the India-hosted site is slow. What can you do?MediumHard to answer
Blob uploads must trigger thumbnail generation automatically. Which services?MediumHard to answer

Azure Databases (SQL, Cosmos DB)15 questions · 9 must-know

Azure SQL Database vs Managed Instance vs SQL Server on a VM?★ Must knowEasy to answer
What is the difference between DTU and vCore models?★ Must knowEasy to answer
How do you connect an App Service to Azure SQL without storing a password?★ Must knowEasy to answer
What are failover groups and how are they different from active geo-replication?★ Must knowMedium to answer
How does backup and restore work in Azure SQL Database?★ Must knowMedium to answer
What is a partition key in Cosmos DB and how do you choose it?★ Must knowMedium to answer
What are Request Units (RU/s) and consistency levels in Cosmos DB?★ Must knowMedium to answer
You need to migrate a 500 GB on-prem SQL Server database with SQL Agent jobs and cross-database queries to Azure with minimal downtime. What do you choose?★ Must knowHard to answer
An Azure SQL database is at 100 % CPU after a release. What do you do?★ Must knowHard to answer
What is serverless compute in Azure SQL Database?MediumMedium to answer
How do you secure Azure SQL Database?MediumMedium to answer
What is an elastic pool and when should you not use it?MediumMedium to answer
What is Hyperscale and when would you use it?MediumHard to answer
Why must applications use retry logic with Azure SQL?MediumHard to answer
A multi-tenant SaaS has 300 small customer databases with different peak times. How do you host them cost-effectively?MediumHard to answer

Amazon Web Services (AWS)16 questions · 10 must-know

What are regions and availability zones?★ Must knowEasy to answer
Explain the shared responsibility model.★ Must knowEasy to answer
What is IAM and what is the difference between a user and a role?★ Must knowEasy to answer
EC2 vs Elastic Beanstalk vs ECS/Fargate vs Lambda for hosting a .NET API?★ Must knowEasy to answer
What is S3 and what are storage classes?★ Must knowEasy to answer
How do you host SQL Server on AWS?★ Must knowMedium to answer
Security group vs network ACL?★ Must knowMedium to answer
SQS vs SNS vs EventBridge?★ Must knowMedium to answer
What is DynamoDB and how do you design keys?★ Must knowMedium to answer
Your ASP.NET Core API on ECS must read files from S3 and connect to RDS SQL Server. How do you set up access securely?★ Must knowHard to answer
ALB vs NLB vs API Gateway?MediumMedium to answer
How do you manage secrets for a .NET app on AWS?MediumMedium to answer
How do you make an application highly available on AWS?MediumHard to answer
What are the pillars of the AWS Well-Architected Framework?MediumHard to answer
A company is moving from Azure to AWS. How would you map their stack (App Service, Azure SQL, Blob, Service Bus, Key Vault, App Insights)?MediumHard to answer
Your AWS bill doubled this month. How do you investigate and reduce it?MediumHard to answer

Google Cloud (GCP)15 questions · 7 must-know

What is the GCP resource hierarchy?★ Must knowEasy to answer
What is Cloud Run and why is it popular for .NET APIs?★ Must knowEasy to answer
What are service accounts?★ Must knowEasy to answer
How do you connect a Cloud Run service to Cloud SQL for SQL Server securely?★ Must knowMedium to answer
Pub/Sub vs Cloud Tasks?★ Must knowMedium to answer
What is BigQuery and when would you use it?★ Must knowMedium to answer
You need to deploy an ASP.NET Core API with a SQL Server database on GCP with minimal operations work. What do you build?★ Must knowHard to answer
Compute Engine vs Cloud Run vs GKE vs App Engine?MediumEasy to answer
What are regions, zones and multi-regions in GCP?MediumEasy to answer
Cloud SQL vs Spanner vs Firestore vs Bigtable?MediumMedium to answer
How is a GCP VPC different from AWS/Azure networks?MediumMedium to answer
How do you control access to a Cloud Run service?MediumMedium to answer
How do you avoid service account keys in CI/CD?MediumHard to answer
Logs from your .NET app on Cloud Run show up as plain text without severity. How do you fix it?MediumHard to answer
BigQuery costs are high because analysts run large queries. How do you reduce them?MediumHard to answer

4. Frontend

HTML & CSS18 questions · 9 must-know

What is semantic HTML and why is it important?★ Must knowEasy to answer
Explain the CSS box model. What does box-sizing: border-box do?★ Must knowEasy to answer
What is CSS specificity? Which rule wins?★ Must knowEasy to answer
Flexbox vs Grid — when do you use each?★ Must knowEasy to answer
How do you centre a div horizontally and vertically?★ Must knowEasy to answer
How do you make a website responsive?★ Must knowMedium to answer
What are media queries and container queries?★ Must knowMedium to answer
How do you make a web page accessible?★ Must knowMedium to answer
The layout looks fine on desktop but has a horizontal scrollbar on mobile. How do you find and fix it?★ Must knowHard to answer
Difference between display: none, visibility: hidden and opacity: 0?MediumEasy to answer
What are the different position values?MediumEasy to answer
What is the difference between em, rem, %, vw and px?MediumMedium to answer
CSS variables vs Sass variables?MediumMedium to answer
What is the critical rendering path and how do you optimise it?MediumMedium to answer
What is a stacking context and why does z-index sometimes not work?MediumHard to answer
What are Core Web Vitals?MediumHard to answer
A designer wants a card grid that shows 1 column on phones, 2 on tablets and 4 on desktop. Write the CSS.MediumHard to answer
Your page jumps around while loading (high CLS). What do you fix?MediumHard to answer

JavaScript24 questions · 17 must-know

What is the difference between == and ===?★ Must knowEasy to answer
What is the difference between var, let and const?★ Must knowEasy to answer
What is hoisting?★ Must knowEasy to answer
What are the primitive data types in JavaScript?★ Must knowEasy to answer
What is the difference between null and undefined?★ Must knowEasy to answer
What are arrow functions and how are they different from regular functions?★ Must knowEasy to answer
What is a closure? Give a practical example.★ Must knowMedium to answer
Explain the event loop.★ Must knowMedium to answer
What is a Promise? Explain Promise.all, allSettled, race and any.★ Must knowMedium to answer
How does this work in JavaScript?★ Must knowMedium to answer
What is the difference between call, apply and bind?★ Must knowMedium to answer
What is prototypal inheritance?★ Must knowMedium to answer
What is event delegation and why use it?★ Must knowMedium to answer
Debounce vs throttle — implement one.★ Must knowMedium to answer
What causes memory leaks in JavaScript and how do you find them?★ Must knowHard to answer
A search box calls the API on every keystroke and floods the server. How do you fix it?★ Must knowHard to answer
A page becomes unresponsive while processing a 50 MB JSON file in the browser. What do you do?★ Must knowHard to answer
What is the difference between shallow copy and deep copy?MediumMedium to answer
What is the difference between map, forEach, filter and reduce?MediumMedium to answer
What are async and defer on script tags?MediumMedium to answer
What is the output of this code and why? for (var i=0;i<3;i++){ setTimeout(()=>console.log(i),0) }MediumHard to answer
What is the difference between interface and type in TypeScript?MediumHard to answer
Users report the app gets slower the longer it's open. How do you investigate?MediumHard to answer
You need to call 3 independent APIs and show the page when all are done, but still show partial data if one fails. How?MediumHard to answer

TypeScript16 questions · 9 must-know

What is TypeScript and why use it over JavaScript?★ Must knowEasy to answer
What is the difference between interface and type?★ Must knowEasy to answer
any vs unknown vs never?★ Must knowEasy to answer
What are union types and how do you narrow them?★ Must knowEasy to answer
What are generics? Give an example.★ Must knowMedium to answer
Explain Partial, Pick, Omit and Record with use cases.★ Must knowMedium to answer
What does strict mode enable and why should it be on?★ Must knowMedium to answer
What is a discriminated union?★ Must knowMedium to answer
The API returned a different JSON shape and the app crashed even though it compiled. Why, and how do you prevent it?★ Must knowHard to answer
What is type inference?MediumEasy to answer
What is the difference between as (type assertion) and satisfies?MediumMedium to answer
What are declaration files (.d.ts)?MediumMedium to answer
What are mapped and conditional types?MediumHard to answer
Structural vs nominal typing — what does TypeScript use?MediumHard to answer
You are migrating a large JavaScript project to TypeScript. How do you do it?MediumHard to answer
Write a type-safe function that groups an array by a key.MediumHard to answer

Node.js17 questions · 11 must-know

What is Node.js and why is it fast for I/O-heavy apps?★ Must knowEasy to answer
Explain the event loop in Node.js.★ Must knowEasy to answer
Is Node.js single-threaded?★ Must knowEasy to answer
What is the difference between CommonJS and ES modules?★ Must knowEasy to answer
What is middleware in Express?★ Must knowEasy to answer
process.nextTick vs setImmediate vs setTimeout(fn, 0)?★ Must knowMedium to answer
How do you handle errors in async Node.js code?★ Must knowMedium to answer
How do you connect Node.js to SQL Server?★ Must knowMedium to answer
What are streams and why are they useful?★ Must knowMedium to answer
What causes event-loop blocking and how do you detect and fix it?★ Must knowHard to answer
Your Node API becomes very slow when a user uploads a large CSV for import. What's wrong and how do you fix it?★ Must knowHard to answer
What are package.json, package-lock.json, dependencies and devDependencies?MediumEasy to answer
What is the cluster module and how is it different from worker threads?MediumMedium to answer
How do you secure an Express API?MediumMedium to answer
How do memory leaks happen in Node and how do you find them?MediumHard to answer
Node.js vs ASP.NET Core — when would you choose each?MediumHard to answer
The production Node process crashes occasionally with "UnhandledPromiseRejection". What do you do?MediumHard to answer

jQuery16 questions · 10 must-know

What is jQuery and why was it popular?★ Must knowEasy to answer
What is the difference between $(document).ready() and window.onload?★ Must knowEasy to answer
What is the $ sign in jQuery? What does noConflict do?★ Must knowEasy to answer
What is the difference between .text(), .html() and .val()?★ Must knowEasy to answer
What is the difference between .on(), .bind(), .live() and .delegate()?★ Must knowMedium to answer
What is event delegation in jQuery and why use it?★ Must knowMedium to answer
What is the difference between .attr() and .prop()?★ Must knowMedium to answer
How do you make AJAX calls with jQuery? What are deferreds?★ Must knowMedium to answer
Click handlers don't work for table rows added after an AJAX refresh. Why and how to fix?★ Must knowHard to answer
An old site uses jQuery 1.11 and a security scan flags XSS vulnerabilities. What do you do?★ Must knowHard to answer
What is method chaining?MediumEasy to answer
What is the difference between .remove(), .detach() and .empty()?MediumMedium to answer
How do you write a jQuery plugin?MediumMedium to answer
How do you re-enable unobtrusive validation for a form loaded via AJAX?MediumHard to answer
Should a new project use jQuery? How would you migrate away from it?MediumHard to answer
A page with 5,000 rows is slow when appending rows in a loop with $("#tbody").append(...). How do you speed it up?MediumHard to answer

AngularJS (legacy)16 questions · 11 must-know

What is AngularJS and how is it different from Angular?★ Must knowEasy to answer
What is two-way data binding in AngularJS?★ Must knowEasy to answer
What are directives? Name some built-in ones.★ Must knowEasy to answer
What is $scope? What is $rootScope?★ Must knowEasy to answer
What is the difference between service, factory and provider?★ Must knowMedium to answer
Explain the digest cycle. When do you need $apply?★ Must knowMedium to answer
How does dependency injection work in AngularJS? What breaks it during minification?★ Must knowMedium to answer
How do you improve the performance of a slow AngularJS app?★ Must knowHard to answer
How would you migrate a large AngularJS app to Angular?★ Must knowHard to answer
You change a model value inside a jQuery datepicker callback but the view doesn't update. Why?★ Must knowHard to answer
An ng-repeat over 3,000 rows makes the page freeze on every keystroke in a search box. Fix it.★ Must knowHard to answer
What is the difference between ng-if and ng-show?MediumEasy to answer
What are the scope binding types in a component/directive (@, =, <, &)?MediumMedium to answer
What is the difference between $emit and $broadcast?MediumMedium to answer
What are filters? How do you create a custom filter?MediumMedium to answer
Your company still runs a business-critical AngularJS app. What risks do you raise and what plan do you propose?MediumHard to answer

Angular24 questions · 17 must-know

What is Angular and how is it different from AngularJS?★ Must knowEasy to answer
What are components and what is a standalone component?★ Must knowEasy to answer
Explain the types of data binding in Angular.★ Must knowEasy to answer
What are directives? Types of directives?★ Must knowEasy to answer
What are pipes? Pure vs impure?★ Must knowEasy to answer
Explain the component lifecycle hooks.★ Must knowMedium to answer
What is dependency injection in Angular? What does providedIn: 'root' mean?★ Must knowMedium to answer
Observable vs Promise?★ Must knowMedium to answer
switchMap vs mergeMap vs concatMap vs exhaustMap?★ Must knowMedium to answer
What are signals and why were they introduced?★ Must knowMedium to answer
Template-driven vs reactive forms — which do you use?★ Must knowMedium to answer
How do you implement route guards and lazy loading?★ Must knowMedium to answer
Explain change detection. What does OnPush do? What is zoneless?★ Must knowHard to answer
How do you prevent memory leaks in Angular?★ Must knowHard to answer
A list of 10,000 rows renders slowly and scrolling lags. How do you optimise?★ Must knowHard to answer
Your search box sends a request on every keystroke and results sometimes appear out of order. Fix it.★ Must knowHard to answer
After login, some API calls still go out without the token, and expired tokens cause random 401s. How do you design auth handling?★ Must knowHard to answer
What is the Angular CLI? Name common commands.MediumEasy to answer
How do components communicate?MediumMedium to answer
What is an HTTP interceptor?MediumMedium to answer
What is SSR and hydration in Angular?MediumHard to answer
What is NgRx and when should you use it?MediumHard to answer
You get "ExpressionChangedAfterItHasBeenCheckedError". What does it mean and how do you fix it?MediumHard to answer
How would you upgrade an Angular 12 app to the latest version?MediumHard to answer

React22 questions · 15 must-know

What is React and what are its main features?★ Must knowEasy to answer
What is JSX?★ Must knowEasy to answer
What is the virtual DOM and reconciliation?★ Must knowEasy to answer
What is the difference between props and state?★ Must knowEasy to answer
Why are keys important in lists?★ Must knowEasy to answer
Explain useEffect and its dependency array. How do you clean up?★ Must knowMedium to answer
What are the Rules of Hooks and why do they exist?★ Must knowMedium to answer
useMemo vs useCallback vs React.memo?★ Must knowMedium to answer
What is the Context API? When would you not use it?★ Must knowMedium to answer
useState vs useReducer?★ Must knowMedium to answer
What is lifting state up?★ Must knowMedium to answer
How do you optimise the performance of a React application?★ Must knowHard to answer
What are React Server Components and how do they differ from SSR?★ Must knowHard to answer
A dashboard with many widgets re-renders entirely when the user types in a search box. How do you fix it?★ Must knowHard to answer
Fetching data in useEffect sometimes shows results for the previous user ID after switching quickly. Why and how to fix?★ Must knowHard to answer
Controlled vs uncontrolled components?MediumEasy to answer
What are custom hooks? Give an example.MediumMedium to answer
What are error boundaries?MediumMedium to answer
What's new in React 18 and 19?MediumHard to answer
What causes infinite re-render loops and how do you fix them?MediumHard to answer
How would you structure a large React application?MediumHard to answer
A modal rendered inside a card is cut off by overflow: hidden on the card. How do you fix it in React?MediumHard to answer

Next.js15 questions · 7 must-know

What is Next.js and how is it different from React?★ Must knowEasy to answer
Explain the App Router folder structure and special files.★ Must knowEasy to answer
What are Server Components and Client Components?★ Must knowEasy to answer
What rendering strategies does Next.js support?★ Must knowMedium to answer
What are Server Actions and what must you be careful about?★ Must knowMedium to answer
How do you connect Next.js to SQL Server safely?★ Must knowMedium to answer
A product listing page is slow because it queries SQL Server on every request, but prices change only once a day. What do you do?★ Must knowHard to answer
What is the difference between next/link and <a>?MediumEasy to answer
What is middleware (proxy in Next 16) used for?MediumMedium to answer
How does Next.js help SEO?MediumMedium to answer
How do you handle environment variables in Next.js?MediumMedium to answer
Pages Router vs App Router?MediumHard to answer
What is hydration and what causes hydration errors?MediumHard to answer
After deployment, a page shows stale data even after the database changed. Why?MediumHard to answer
Your Next.js app works locally but database calls fail on Vercel. What do you check?MediumHard to answer

Vue.js21 questions · 14 must-know

What is Vue.js and why is it called progressive?★ Must knowEasy to answer
What are the most commonly used Vue directives?★ Must knowEasy to answer
What is the difference between v-if and v-show?★ Must knowEasy to answer
What are computed properties and how are they different from methods and watchers?★ Must knowEasy to answer
What is the purpose of the key attribute in v-for?★ Must knowEasy to answer
Explain ref vs reactive.★ Must knowMedium to answer
How does reactivity work in Vue 3? How is it different from Vue 2?★ Must knowMedium to answer
Options API vs Composition API — which and why?★ Must knowMedium to answer
What are the lifecycle hooks in Vue 3?★ Must knowMedium to answer
What are slots and scoped slots?★ Must knowMedium to answer
What is Pinia and how does it compare to Vuex?★ Must knowMedium to answer
What are composables and how do they differ from mixins?★ Must knowHard to answer
A page with a list of 20,000 items is slow to render and scroll. How do you fix it?★ Must knowHard to answer
You destructure props or a reactive store and the UI stops updating. Why?★ Must knowHard to answer
How do you pass data between parent and child components?MediumEasy to answer
What is provide/inject?MediumMedium to answer
How do navigation guards work in Vue Router?MediumMedium to answer
What is nextTick and when do you need it?MediumHard to answer
How does Vue's compiler optimise rendering?MediumHard to answer
Your company has a large Vue 2 app. Vue 2 reached EOL in December 2023. What's your plan?MediumHard to answer
A watcher calling an API fires too often while the user types. How do you control it?MediumHard to answer

5. Automation & Industry 4.0

Test Automation19 questions · 13 must-know

What is the test pyramid and why does it matter?★ Must knowEasy to answer
What should and shouldn't be automated?★ Must knowEasy to answer
Which Selenium locators do you use and in what order?★ Must knowEasy to answer
Implicit vs explicit vs fluent wait?★ Must knowEasy to answer
What is the Page Object Model?★ Must knowEasy to answer
Selenium vs Playwright — which would you choose?★ Must knowMedium to answer
How do you handle StaleElementReferenceException?★ Must knowMedium to answer
How do you design an automation framework from scratch?★ Must knowMedium to answer
How do you test REST APIs? What do you validate?★ Must knowMedium to answer
How do you run UI tests in parallel safely?★ Must knowHard to answer
How do you integrate automated tests into CI/CD?★ Must knowHard to answer
Your regression suite of 800 UI tests takes 6 hours and 10% fail randomly. What do you do?★ Must knowHard to answer
A test passes locally but fails in the CI pipeline. How do you investigate?★ Must knowHard to answer
What is data-driven testing?MediumMedium to answer
How do you handle iframes, multiple windows, alerts and dropdowns in Selenium?MediumMedium to answer
What is BDD and when is it worth it?MediumMedium to answer
What metrics do you track for test automation?MediumHard to answer
The developers change the UI often and your locators break every sprint. How do you fix this?MediumHard to answer
How would you test a login page? List the cases.MediumHard to answer

Industrial Automation (PLC/SCADA)18 questions · 13 must-know

What is a PLC and how is it different from a microcontroller or PC?★ Must knowEasy to answer
Explain the PLC scan cycle.★ Must knowEasy to answer
What are the IEC 61131-3 programming languages?★ Must knowEasy to answer
What is the difference between SCADA, HMI and DCS?★ Must knowEasy to answer
Why is 4–20 mA used instead of 0–20 mA or 0–10 V?★ Must knowEasy to answer
Explain the start/stop seal-in (latching) circuit.★ Must knowMedium to answer
Explain TON, TOF and counters with an example.★ Must knowMedium to answer
What is Modbus? Explain its data model and function codes.★ Must knowMedium to answer
What is OPC UA and why is it important for Industry 4.0?★ Must knowMedium to answer
How would you collect data from 50 PLCs of different brands into a .NET application?★ Must knowHard to answer
How do you secure an OT network?★ Must knowHard to answer
A motor sometimes doesn't start when the operator presses Start on the HMI. How do you troubleshoot?★ Must knowHard to answer
The MES shows wrong temperature values from a Modbus device. What could be wrong?★ Must knowHard to answer
What is the difference between NO and NC contacts, and why is a stop button wired NC?MediumEasy to answer
What is PID control? What do P, I and D do?MediumMedium to answer
What is the difference between FAT and SAT?MediumMedium to answer
What is the difference between a standard PLC and a safety PLC?MediumHard to answer
Management wants to let a cloud dashboard write setpoints directly to PLCs. What do you advise?MediumHard to answer

Industry 4.0 & IIoT19 questions · 12 must-know

What is Industry 4.0?★ Must knowEasy to answer
What is IIoT and how is it different from consumer IoT?★ Must knowEasy to answer
What is OEE and how is it calculated?★ Must knowEasy to answer
What is an MES and how does it differ from ERP?★ Must knowEasy to answer
What is MQTT and why is it popular in IIoT?★ Must knowMedium to answer
Explain MQTT QoS levels.★ Must knowMedium to answer
What is the difference between OPC UA and MQTT? When do you use which?★ Must knowMedium to answer
What is edge computing and why is it needed in factories?★ Must knowMedium to answer
How does predictive maintenance work? What data do you need?★ Must knowHard to answer
Design a real-time OEE dashboard for 20 production lines.★ Must knowHard to answer
A plant has 30-year-old machines without network connectivity. How do you bring them into an Industry 4.0 project?★ Must knowHard to answer
OEE dashboards show 110 % performance on some lines. What is wrong?★ Must knowHard to answer
What is ISA-95?MediumEasy to answer
What is the Unified Namespace?MediumMedium to answer
What are MTBF and MTTR?MediumMedium to answer
What is a digital twin? Give a practical example.MediumHard to answer
How do you handle millions of telemetry rows per day in SQL Server?MediumHard to answer
Telemetry arrives late and out of order after network outages. How do you keep reports correct?MediumHard to answer
Management asks: "How do we start Industry 4.0 with a small budget?"MediumHard to answer

6. Web3 & Blockchain

Blockchain & Web319 questions · 12 must-know

What is blockchain? Explain it simply.★ Must knowEasy to answer
What is Web3 and how is it different from Web2?★ Must knowEasy to answer
What is a hash and why is it important in blockchain?★ Must knowEasy to answer
What is the difference between a public and a private blockchain?★ Must knowEasy to answer
What is a smart contract?★ Must knowEasy to answer
Proof of Work vs Proof of Stake?★ Must knowMedium to answer
Explain gas and EIP-1559.★ Must knowMedium to answer
What are ERC-20 and ERC-721?★ Must knowMedium to answer
What are layer 2 solutions? Optimistic vs ZK rollups?★ Must knowMedium to answer
How would you build a backend in .NET that confirms crypto payments?★ Must knowHard to answer
A user says their tokens were stolen even though they never shared their seed phrase. What likely happened, and how could the dApp have protected them?★ Must knowHard to answer
Your company wants to "put the supply chain on the blockchain". How do you evaluate it?★ Must knowHard to answer
What is a wallet? What happens if you lose your seed phrase?MediumEasy to answer
What is the difference between the UTXO model and the account model?MediumMedium to answer
What is an oracle and why is it needed?MediumMedium to answer
What is the blockchain trilemma?MediumMedium to answer
What are MEV and front-running?MediumHard to answer
When should you NOT use a blockchain?MediumHard to answer
Transactions from your backend keep failing with "nonce too low" or get stuck pending. How do you fix it?MediumHard to answer

Solidity19 questions · 13 must-know

What is Solidity and what is the EVM?★ Must knowEasy to answer
Explain function visibility in Solidity.★ Must knowEasy to answer
What is the difference between view and pure functions?★ Must knowEasy to answer
What are storage, memory and calldata?★ Must knowEasy to answer
What is msg.sender vs tx.origin?★ Must knowEasy to answer
What is a reentrancy attack and how do you prevent it?★ Must knowMedium to answer
require vs revert vs assert vs custom errors?★ Must knowMedium to answer
How do you send Ether from a contract? transfer vs send vs call?★ Must knowMedium to answer
What changed in Solidity 0.8?★ Must knowMedium to answer
How do upgradeable contracts work? What are the risks?★ Must knowHard to answer
How do you reduce gas costs in a contract?★ Must knowHard to answer
You must build a token sale contract that accepts USDC and gives buyers your token. What would you check for security?★ Must knowHard to answer
A deployed contract has a bug that can drain funds, and it's not upgradeable. What do you do?★ Must knowHard to answer
What are events and why use them?MediumEasy to answer
What is the difference between an interface, an abstract contract and a library?MediumMedium to answer
What are modifiers? Give an example.MediumMedium to answer
Why is on-chain randomness hard, and how do you get it?MediumHard to answer
What is the difference between call, delegatecall and staticcall?MediumHard to answer
Your NFT mint is expensive and fails for some buyers because of gas. How do you improve it?MediumHard to answer

7. Interview Questions & Career

.NET Full Stack Interview26 questions · 18 must-know

Explain the architecture of your current project end to end.★ Must knowEasy to answer
What happens when a user clicks "Save" in your Angular/React app until the data is in SQL Server?★ Must knowEasy to answer
What is the difference between authentication and authorization? Which status codes do they return?★ Must knowEasy to answer
What is CORS and why do you get a CORS error only in the browser?★ Must knowEasy to answer
Why do you return DTOs instead of EF entities from an API?★ Must knowEasy to answer
How do you implement paging, sorting and searching in a full stack app?★ Must knowMedium to answer
Where do you store the JWT in an SPA, and how do you refresh it?★ Must knowMedium to answer
How do you handle errors globally in both the API and the UI?★ Must knowMedium to answer
Explain the N+1 problem and how you detect and fix it.★ Must knowMedium to answer
How do you make an API call from Angular and show loading and error states?★ Must knowMedium to answer
How do you secure an ASP.NET Core Web API?★ Must knowMedium to answer
How would you structure a new .NET full stack solution from scratch?★ Must knowHard to answer
Your list page takes 8 seconds to load. How do you find and fix the problem?★ Must knowHard to answer
Monolith or microservices for a new product? Justify.★ Must knowHard to answer
The UI shows "CORS error" after you deployed the API to Azure, but it worked locally. What do you check?★ Must knowHard to answer
A user can see another customer's orders by changing the id in the URL. What is wrong and how do you fix it?★ Must knowHard to answer
After a release the API is slow and SQL CPU is at 100%. What do you do?★ Must knowHard to answer
You are asked to add a "bulk upload products from Excel" feature. Walk through your design.★ Must knowHard to answer
How do you handle two users editing the same record at the same time?MediumMedium to answer
How do you manage configuration and secrets across dev, QA and production?MediumMedium to answer
What does your CI/CD pipeline do for a full stack app?MediumMedium to answer
How do you keep the API and the frontend contract in sync?MediumHard to answer
How do you run long work (reports, emails, imports) without blocking the user?MediumHard to answer
Two services need the same customer data. One team proposes sharing one database table. What do you advise?MediumHard to answer
Your Angular/React app works locally but shows a blank page after deployment. How do you debug it?MediumHard to answer
An order must be saved, stock reduced and an email sent. How do you keep these consistent?MediumHard to answer

HR & Behavioural25 questions · 15 must-know

Tell me about yourself.★ Must knowEasy to answer
Why should we hire you?★ Must knowEasy to answer
What are your strengths?★ Must knowEasy to answer
What is your greatest weakness?★ Must knowEasy to answer
Why do you want to work here?★ Must knowEasy to answer
Why are you leaving your current company?★ Must knowEasy to answer
Where do you see yourself in five years?★ Must knowEasy to answer
Tell me about a time you had a conflict with a colleague.★ Must knowMedium to answer
Tell me about a failure or mistake you made.★ Must knowMedium to answer
Describe a situation where you worked under pressure or a tight deadline.★ Must knowMedium to answer
Tell me about your biggest achievement.★ Must knowMedium to answer
How do you handle criticism or negative feedback?★ Must knowMedium to answer
How do you prioritise when you have multiple tasks?★ Must knowMedium to answer
You are offered a role, but another company is also likely to make an offer next week. What do you do?★ Must knowHard to answer
Your manager asks you to finish a task that you believe will cause a production problem. What do you do?★ Must knowHard to answer
What do you know about our company?MediumEasy to answer
Are you willing to relocate or work in shifts?MediumEasy to answer
What is your notice period? Can you join earlier?MediumEasy to answer
What motivates you?MediumMedium to answer
Do you prefer working alone or in a team?MediumMedium to answer
Have you ever disagreed with your manager? What happened?MediumMedium to answer
How do you keep your skills up to date?MediumMedium to answer
Tell me about a time you went beyond your job description.MediumHard to answer
A teammate isn't contributing and you're doing their work. How do you handle it?MediumHard to answer
What would you do in your first 30–60–90 days here?MediumHard to answer

Team Lead & Agile24 questions · 16 must-know

What is the difference between a tech lead and an engineering manager?★ Must knowEasy to answer
Explain Scrum roles, events and artifacts.★ Must knowEasy to answer
What is the difference between Agile and Waterfall?★ Must knowEasy to answer
How do you estimate a project or a large feature?★ Must knowMedium to answer
How do you delegate work in your team?★ Must knowMedium to answer
How do you mentor junior developers?★ Must knowMedium to answer
How do you handle a team member who is underperforming?★ Must knowMedium to answer
How do you resolve a conflict between two team members?★ Must knowMedium to answer
How do you handle scope changes requested in the middle of a sprint?★ Must knowMedium to answer
How do you report project status to stakeholders?★ Must knowMedium to answer
How do you make architecture or technology decisions in a team?★ Must knowHard to answer
How do you measure your team's performance?★ Must knowHard to answer
Your project is two weeks from the deadline and you realise it will be late by one week. What do you do?★ Must knowHard to answer
A critical production issue occurs on Friday evening. Walk me through how you handle it.★ Must knowHard to answer
The client keeps adding requirements without changing the deadline. How do you manage it?★ Must knowHard to answer
Your best developer resigns in the middle of a critical release. What do you do?★ Must knowHard to answer
What are story points and velocity?MediumEasy to answer
Scrum vs Kanban — when would you use each?MediumEasy to answer
What do you do in a sprint retrospective that has become boring and repetitive?MediumMedium to answer
How do you handle technical debt?MediumMedium to answer
How would you build and scale a new team from 3 to 10 developers?MediumHard to answer
Two senior developers disagree strongly on using microservices versus a modular monolith for a new product. How do you decide?MediumHard to answer
A team member is consistently working late and seems burned out. What do you do?MediumHard to answer
You are asked to lead a team working on a technology you don't know well. How do you approach it?MediumHard to answer

Career Gaps & Salary15 questions · 8 must-know

I see a gap of a year in your resume. Can you explain it?★ Must knowEasy to answer
What is your expected salary?★ Must knowEasy to answer
What is your current CTC and why do you expect a big hike?★ Must knowEasy to answer
You were laid off. Was it because of performance?★ Must knowMedium to answer
How do you justify switching from support/testing to development?★ Must knowMedium to answer
We can offer only 15% above your current salary. Will you accept?★ Must knowMedium to answer
You receive a written offer below your expectation, but you really want the job. What do you do?★ Must knowHard to answer
Background verification shows a mismatch in your previous employment dates. What should you do?★ Must knowHard to answer
Why did you change jobs so frequently?MediumEasy to answer
Are you open to negotiation on the salary you mentioned?MediumEasy to answer
Do you have other offers?MediumMedium to answer
What is your notice period, and will you be able to join early?MediumMedium to answer
How would you respond to a counter-offer from your current employer?MediumHard to answer
You were freelancing for two years. The interviewer worries you won't fit into a team. How do you answer?MediumHard to answer
An HR person asks for your expected salary before the technical rounds, and the posting has no range. What do you say?MediumHard to answer

Company-wise Prep16 questions · 11 must-know

(IT services) Explain your current project and your role in it.★ Must knowEasy to answer
(IT services) Why do you want to join a services company like ours?★ Must knowEasy to answer
(IT services) Are you comfortable working in different shifts, technologies or locations?★ Must knowEasy to answer
(Freshers) What happens in online assessments like TCS NQT or similar tests, and how do you prepare?★ Must knowEasy to answer
(Amazon) Tell me about a time you disagreed with your manager or team. (Have Backbone; Disagree and Commit)★ Must knowMedium to answer
(Amazon) Tell me about a time you obsessed over a customer. (Customer Obsession)★ Must knowMedium to answer
(Amazon) Tell me about a time you had to dive deep to solve a problem. (Dive Deep)★ Must knowMedium to answer
(Microsoft/Google) How do you approach a coding interview problem?★ Must knowMedium to answer
(Product companies) Design a URL shortener.★ Must knowMedium to answer
You have interviews with a services company and a product company in the same week. How do you prepare differently?★ Must knowHard to answer
You failed a round at a company you really wanted. What do you do next?★ Must knowHard to answer
(Consulting) The client says your team's delivery quality is poor. How do you respond?MediumMedium to answer
(Startups) You get a 4-hour take-home: build a small task-management API. What do you prioritise?MediumMedium to answer
(Taiwan) Why do you want to work in Taiwan, and how do you handle the language?MediumMedium to answer
(GCC) How would you work effectively with a team spread across India, Europe and the US?MediumHard to answer
A recruiter from a big brand offers a role with a lower title and similar pay. Should you accept?MediumHard to answer

All Interview Questions — Topic-wise

0. Fundamentals

How Computers & Memory Work16 questions · 7 must-know

Data Structures & Algorithms16 questions · 11 must-know

Coding Round (DSA)23 questions · 16 must-know

Networking & Hosting: How the Web Works18 questions · 11 must-know

System Design (HLD)17 questions · 13 must-know

Low-Level Design (LLD)16 questions · 9 must-know

1. .NET

C#48 questions · 23 must-know

VB.NET16 questions · 8 must-know

.NET Internals: CLR, Memory & GC19 questions · 12 must-know

OOP22 questions · 12 must-know

SOLID Principles15 questions · 8 must-know

Design Patterns21 questions · 13 must-know

ADO.NET18 questions · 12 must-know

LINQ21 questions · 13 must-know

Entity Framework (EF6 & Core)23 questions · 14 must-know

Dapper15 questions · 8 must-know

ASP.NET Web Forms17 questions · 11 must-know

ASP.NET MVC 516 questions · 10 must-know

Modern .NET: Host, Config, DI17 questions · 10 must-know

ASP.NET Core MVC23 questions · 14 must-know

ASP.NET Core Web API25 questions · 17 must-know

Exception Handling & Custom Errors16 questions · 10 must-know

Logging & Custom Logging16 questions · 7 must-know

Custom Controls & Components16 questions · 6 must-know

Project Architecture & Folders15 questions · 7 must-know

Clean Code & Unit Testing18 questions · 10 must-know

Microservices & System Design20 questions · 14 must-know

2. Database, ETL & BI

SQL Server & T-SQL30 questions · 21 must-know

SQL Server Internals18 questions · 12 must-know

ETL & Data Warehouse19 questions · 11 must-know

SSIS21 questions · 13 must-know

SSRS18 questions · 10 must-know

3. Cloud & DevOps

IIS & Hosting .NET Apps16 questions · 10 must-know

Git & GitHub19 questions · 11 must-know

Docker18 questions · 11 must-know

Kubernetes21 questions · 14 must-know

Azure DevOps CI/CD18 questions · 11 must-know

Microsoft Azure20 questions · 13 must-know

Azure Databases (SQL, Cosmos DB)15 questions · 9 must-know

Amazon Web Services (AWS)16 questions · 10 must-know

Google Cloud (GCP)15 questions · 7 must-know

4. Frontend

HTML & CSS18 questions · 9 must-know

JavaScript24 questions · 17 must-know

TypeScript16 questions · 9 must-know

Node.js17 questions · 11 must-know

jQuery16 questions · 10 must-know

AngularJS (legacy)16 questions · 11 must-know

Angular24 questions · 17 must-know

React22 questions · 15 must-know

Next.js15 questions · 7 must-know

Vue.js21 questions · 14 must-know

5. Automation & Industry 4.0

Test Automation19 questions · 13 must-know

Industrial Automation (PLC/SCADA)18 questions · 13 must-know

Industry 4.0 & IIoT19 questions · 12 must-know

6. Web3 & Blockchain

Blockchain & Web319 questions · 12 must-know

Solidity19 questions · 13 must-know

7. Interview Questions & Career

.NET Full Stack Interview26 questions · 18 must-know

HR & Behavioural25 questions · 15 must-know

Team Lead & Agile24 questions · 16 must-know

Career Gaps & Salary15 questions · 8 must-know

Company-wise Prep16 questions · 11 must-know