What design patterns are commonly used in ASP.NET Core middleware?

Short answer: Chain of Responsibility: Middleware components form a pipeline where each decides to pass control or handle the request. Decorator: Middleware wraps around the next component, adding behavior before or after. Factory: Middleware components can be created via factories for configurable pipeline setup.

Real-world example (ShopNest)

Patterns in ShopNest should solve a real pain (swappable payments, test seams)—not be added for decoration.

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.