Caching: response, output, in-memory, distributed, HybridCache — ASP.NET Core Web API & REST

11. Caching: response, output, in-memory, distributed, HybridCache

Intermediate★ Must knowLesson 11 of 15

Cache	Where	Use
HTTP caching headers (`Cache-Control`, `ETag`)	Client/CDN/proxy	Public GET resources
Output caching (.NET 7)	Server memory (or Redis)	Whole responses; tag-based eviction
`IMemoryCache`	Process memory	Single instance, fast
`IDistributedCache` (Redis, SQL)	Shared	Multiple instances / scale-out
`HybridCache` (.NET 9)	L1 memory + L2 distributed	Stampede protection, tags, one API

csharp

builder.Services.AddHybridCache();
public class ProductService(HybridCache cache, AppDbContext db)
{
    public ValueTask<ProductDto?> GetAsync(int id, CancellationToken ct) =>
        cache.GetOrCreateAsync($"product:{id}", async token =>
            await db.Products.Where(p => p.Id == id).Select(p => new ProductDto(p.Id, p.Name, p.Price)).FirstOrDefaultAsync(token),
            cancellationToken: ct);
}

Cache invalidation strategies: expiration (absolute/sliding), explicit removal on write, tags, versioned keys.