Lesson 34 / 34
Key Takeaways
Review the key NestJS ideas: modules, controllers, services, dependency injection and the request lifecycle order.
The NestJS triangle
Modules organize your app, Controllers handle requests, Services contain logic. Everything is tied together by Dependency Injection.
Request lifecycle
Request flow: Middleware → Guards → Interceptors (before) → Pipes → Controller/Handler → Interceptors (after) → Exception filters. Learn this order to debug correctly.
Database patterns
Use DTOs for input; repositories for data access; migrations for schema. Keep business logic in services, queries in repositories.
Final quiz 1 of 8
Final quiz
Quick check: What does a NestJS module do?
- Compiles TypeScript
- Opens database connections only
- Groups related controllers and providers
- Replaces Express
Answer
Groups related controllers and providers — Modules are the unit of organization in a Nest app.
Final quiz 2 of 8
Final quiz
Quick check: How are services normally obtained in a controller?
- new Service()
- Global variables
- require() at runtime
- Constructor dependency injection
Answer
Constructor dependency injection — Nest's IoC container injects providers for you.
Final quiz 3 of 8
Final quiz
Quick check: Which component validates and transforms incoming data?
- Pipe
- Guard
- Filter
- Module
Answer
Pipe — ValidationPipe checks DTOs before the handler runs.
Final quiz 4 of 8
Final quiz
Quick check: Which component decides whether a request may continue (e.g. authorization)?
- Pipe
- Guard
- Interceptor
- Entity
Answer
Guard — Guards implement CanActivate and allow or reject.
Final quiz 5 of 8
Final quiz
Quick check: What is the correct order of the request lifecycle?
- Pipes, Guards, Middleware, Handler
- Handler, Pipes, Guards
- Middleware, Guards, Interceptors, Pipes, Handler
- Guards, Handler, Middleware
Answer
Middleware, Guards, Interceptors, Pipes, Handler — Interceptors run before pipes and again after the handler.
Final quiz 6 of 8
Final quiz
Quick check: What problem does N+1 describe in ORMs?
- Too many migrations
- Too many modules
- Slow compilation
- One query per related row instead of a join or batch
Answer
One query per related row instead of a join or batch — Load relations with a join or batch to avoid it.
Final quiz 7 of 8
Final quiz
Quick check: Which tool versions your database schema in TypeORM?
- Migrations
- Interceptors
- Pipes
- Decorators
Answer
Migrations — Migrations record and replay schema changes.
Final quiz 8 of 8
Final quiz
Quick check: Why use a multi-stage Docker build for NestJS?
- Faster TypeScript
- Smaller final image with only runtime files
- It is required by Nest
- To skip tests
Answer
Smaller final image with only runtime files — Build tools stay in the builder stage; the final image is lean.