Nestjs Interceptors

NestJS Interceptors

Interceptors are @Injectable() classes implementing NestInterceptor. Their intercept(context: ExecutionContext, next: CallHandler) method runs logic before the route handler and transforms the response stream returned by next.handle() using RxJS operators. They are the idiomatic place for cross-cutting concerns — response shaping, logging, timeouts, caching — that should stay out of controllers and services.

When to Apply

Apply these rules when you are:

• Writing or reviewing a class that implements NestInterceptor.
• Wrapping handler responses in a consistent envelope.
• Adding request/response logging or latency measurement.
• Enforcing per-request timeouts.
• Caching GET responses with CacheInterceptor.
• Deciding whether to bind an interceptor globally, per-controller, or per-route.

Do not reach for an interceptor when the work is core business logic — that belongs in a service (see interceptors-not-for-mutation-logic).

Rules

| Rule | Impact | Summary | | --- | --- | --- | | [response-transform-interceptor](rules/response-transform-interceptor.md) | HIGH | Wrap responses in a consistent envelope via map(). | | [logging-interceptor](rules/logging-interceptor.md) | MEDIUM | Measure handler duration with tap(); log method/url/time. | | [timeout-interceptor](rules/timeout-interceptor.md) | HIGH | Fail slow requests with timeout() + RequestTimeoutException. | | [cache-interceptor](rules/cache-interceptor.md) | MEDIUM | Cache GET responses with CacheInterceptor + CacheModule. | | [interceptors-not-for-mutation-logic](rules/interceptors-not-for-mutation-logic.md) | HIGH | Keep business logic in services; interceptors are cross-cutting only. | | [bind-globally-vs-scoped](rules/bind-globally-vs-scoped.md) | MEDIUM | Prefer APP_INTERCEPTOR for DI-friendly global binding. |

How to Use

1. Identify the cross-cutting concern (transform, log, timeout, cache).
2. Open the matching rule file and follow the Correct pattern.
3. Keep intercept() thin — pipe RxJS operators onto next.handle(), never

put domain logic inside.

1. Choose a binding scope with bind-globally-vs-scoped: route, controller, or

global via APP_INTERCEPTOR.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: dkmqflx
• Source: dkmqflx/nestjs-best-practices-plugin
• License: MIT

Install and usage instructions live in the source repository linked above.