NestJS Technology & Digital Applications 4

Question 1

What is the purpose of `@EventPattern()` in a NestJS microservice?

Accepted Answer

It handles fire-and-forget events where no response is expected

Answer

@EventPattern() handles one-way event-based communication in microservices where the publisher doesn't await a response.

Question 2

Which NestJS module scope makes a provider instantiated per request?

Accepted Answer

Scope.REQUEST

Answer

Scope.REQUEST creates a new provider instance for each incoming request, which is useful for per-request state like user context.

Question 3

How do you make a NestJS controller method return a streaming response?

Accepted Answer

Return an Observable from the method and NestJS pipes it to the response

Answer

Returning an RxJS Observable from a handler allows NestJS to subscribe and stream emitted values as a chunked HTTP response.

Question 4

What does enabling `strict mode` in NestJS's ValidationPipe do?

Accepted Answer

Throws on any unrecognized property in the request body

Answer

Setting forbidNonWhitelisted: true (strict mode) causes ValidationPipe to throw a 400 error if the request body contains properties not defined in the DTO.

Question 5

In NestJS, what is the `ExecutionContext` used for in guards and interceptors?

Accepted Answer

Accessing the underlying request/response objects and handler metadata

Answer

ExecutionContext extends ArgumentsHost and provides methods to get the request/response objects and reflect metadata set on route handlers.

NestJS Practice Test

NestJS Practice Test

NestJS Technology & Digital Applications 4