Questions
4 of 6
1How do you implement a @Public() decorator to skip a global auth guard for specific routes in NestJS?
2What is a guard in NestJS and when should you use one over middleware?
3How do you write a single guard that works across both HTTP and WebSocket transports in NestJS?
4How does the request lifecycle behave differently for WebSocket gateways vs HTTP controllers in NestJS?
5How do you implement role-based access control (RBAC) with a guard and Reflector in NestJS?
6What does a guard return when it needs to deny the request and how can it throw a custom exception in NestJS?
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How does the request lifecycle behave differently for WebSocket gateways vs HTTP controllers in NestJS?

WebSocket gateways support guards, interceptors, pipes, and filters but not middleware — middleware is HTTP-only. Guards use ctx.switchToWs().getClient() to access the socket. Exception filters use host.switchToWs(). The same enhancer class can support both HTTP and WebSocket by checking ctx.getType().

WebSocket gateway with guards, pipes, and filters
HTTP vs WebSocket lifecycle differences:
  1. 1

    Middleware — HTTP only; WebSocket connections skip the middleware layer entirely.

  2. 2

    Guards — supported on gateways; use ctx.switchToWs().getClient() for socket access.

  3. 3

    Interceptors — supported on gateways; wrap @SubscribeMessage handlers.

  4. 4

    Pipes — supported on @MessageBody() and @ConnectedSocket() parameters.

  5. 5

    Filters — supported; use host.switchToWs() to access the socket and data.

  6. 6

    WsException should be thrown in WebSocket context instead of HttpException.