Lesson 33 / 33
Key Takeaways
Essential concepts and patterns you should know.
The NestJS triangle
Modules organize your app, Controllers handle requests, Services contain logic. Everything is tied together by Dependency Injection.
Request lifecycle
Middleware → Guards → Pipes → Interceptors (before) → Controller/Handler → Interceptors (after) → Filters. Learn this flow to debug correctly.
Database patterns
Use DTOs for input; repositories for data access; migrations for schema. Keep business logic in services, queries in repositories.