What is the Nest request lifecycle?

Definition:

The request lifecycle is the order in which Nest processes an incoming request and produces a response. Different extension points handle different concerns, such as access checks, input conversion and response wrapping. Knowing the order helps explain why code in one stage cannot rely on work that happens later.

Key points:

• Middleware → guards → interceptors before → pipes → controller/service.

• The response returns through interceptors in reverse order.

• Exception filters handle uncaught errors; they are not a normal success step.

• A guard runs before pipes, so it should not assume route arguments already passed DTO validation.

Interview point:

• Show both inbound and outbound paths; exception filters are used when an uncaught error reaches the exception layer.