How to structure a large ASP.NET Core solution (layers, clean

Short answer: architecture, onion architecture) Use layered architecture: Presentation (API/UI), Application (services, business logic), Domain (entities, business rules), Infrastructure (data access, external services).

Explain a bit more

Clean Architecture emphasizes separation of concerns and dependency direction towards the domain layer. Onion Architecture structures the app around the core domain, with dependencies pointing inward. Use projects to separate concerns and improve maintainability.

Real-world example (ShopNest)

A ShopNest checkout request flows through middleware, hits a minimal API or controller, uses scoped services, and returns ProblemDetails on errors.

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.