How do you apply global middleware, pipes, guards, or interceptors in NestJS?

Use app.useGlobalPipes(), app.useGlobalGuards(), app.useGlobalInterceptors(), and app.useGlobalFilters(). These bypass DI so they cannot inject services. To use DI, register globals inside a module using the APP_GUARD, APP_PIPE, APP_INTERCEPTOR, or APP_FILTER tokens.

Two ways to register global enhancers

Key difference:

1
app.useGlobal*() — simple but cannot inject services; use for dependency-free enhancers.
2
APP_* tokens — registered inside the DI container; supports full constructor injection.
3
The APP_* token approach is preferred for any enhancer that has dependencies.

Difficulty: 6/10

Topics: Middleware, Interceptors, Guards

Scenario Questions

0-2 years experience

1
How would you add a global middleware in NestJS to log every incoming request URL and method?
2
What happens if you register a global guard that always returns false — will any endpoint still work?

2-5 years experience

1
Our global interceptor is modifying the response body, but one endpoint now returns a file stream — the file is corrupted. How do you fix this without removing the interceptor?
2
A teammate added a global pipe that validates all inputs, but now our health check endpoint is failing. How do you exempt it without touching every route?

5-8 years experience

1
We have 15 microservices using NestJS, each with their own global interceptors for logging and metrics — but now we’re seeing performance degradation under load. How would you diagnose and optimize this?
2
How would you design a system where different teams can register their own global interceptors without conflicting, while still maintaining a consistent request/response flow?

8+ years experience

1
We’re migrating from Express to NestJS and have hundreds of legacy routes with custom middleware — how would you architect a phased rollout of global interceptors and guards without breaking existing clients?
2
How would you enforce cross-cutting concerns like authentication and audit logging across multiple NestJS applications owned by different teams, while allowing each team to extend or override behavior safely?

Follow-up Questions

❓What happens if you register a global guard that throws an error before the controller is reached?
❓How would you debug a global interceptor that’s not being called on a specific route?
❓Can you apply a middleware globally but exclude it for certain paths?