How to override default DI behavior (e.g., remove or replace services)

Short answer: To replace: services.AddSingleton<IService, CustomImplementation>(); To remove: var descriptor = services.First(x => x.ServiceType == typeof(IMyService)); services.Remove(descriptor);

Real-world example (ShopNest)

ShopNest registers AppDbContext as Scoped and IMemoryCache as Singleton. Putting DbContext in a Singleton causes threading bugs.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.