Questions
6 of 12
1How do you apply global middleware, pipes, guards, or interceptors in NestJS?
2What is the APP_GUARD / APP_PIPE token pattern in NestJS?
3What is the difference between app.use() and NestJS middleware?
4What is the difference between a service and a repository in NestJS?
5How does NestJS achieve platform agnosticism between Express and Fastify?
6How does the NestJS bootstrap sequence work?
7What is a barrel module in NestJS and when does it become an anti-pattern?
8How does NestJS resolve a provider when the same token is exported by two different imported modules?
9How do you implement a plugin system using dynamic modules in NestJS?
10How does NestJS handle module initialization order and can you control it?
11How do you unit-test a module that uses a dynamic module dependency in NestJS?
12What is the difference between a monorepo and a standard NestJS project structure?
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Decorators
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Dependency Injection
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Architecture
Request Lifecycle
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Exception Handling
API Design
GraphQL
Database and ORM
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Authentication and Authorization
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How does the NestJS bootstrap sequence work?

NestJS bootstrap: NestFactory.create() scans the module graph, builds the DI container, instantiates all singletons, fires OnModuleInit hooks (depth-first), fires OnApplicationBootstrap hooks, then starts the HTTP server. On shutdown: OnModuleDestroy, BeforeApplicationShutdown, then OnApplicationShutdown fire in order.

Full bootstrap sequence:
  1. 1
    1. NestFactory.create(AppModule) is called.
  2. 2
    1. NestJS recursively scans the module graph — resolves all imports, providers, exports.
  3. 3
    1. The IoC container is built; all singleton providers are instantiated.
  4. 4
    1. OnModuleInit lifecycle hook fires for each module (depth-first order).
  5. 5
    1. OnApplicationBootstrap fires for each module.
  6. 6
    1. app.listen() starts the HTTP server — app is now ready to accept requests.
Implementing lifecycle hooks