How do global, controller and route handlers interact?

Definition:

Nest can attach request handlers at global, controller and route scopes. Scope determines which requests a handler applies to, while handler type determines execution order. Interceptors wrap inner work and unwind on the response path; exception filters select a matching handler rather than form a normal middleware chain.

Key points:

• Guards and inbound interceptors generally run global → controller → route.
• Outbound interceptors run route → controller → global.
• Filters start at the closest matching scope; the same error does not pass through every filter.

Reference: Nest request lifecycle.

• Keep ordering-dependent behavior explicit and verify it when multiple decorators or global registrations are involved.

Interview point:

• An interceptor cannot catch an earlier guard failure because it has not started wrapping the handler yet.