NestJS Professional Standards & Competencies 3

Question 1

What is the professional standard for logging in production NestJS applications?

Accepted Answer

Inject the built-in Logger or a structured logger like Winston with appropriate log levels

Answer

Structured logging with configurable log levels enables observability without flooding production logs with debug noise.

Question 2

Which NestJS feature should be used to document and enforce API contracts for REST APIs consumed by external teams?

Accepted Answer

@nestjs/swagger with OpenAPI decorators

Answer

@nestjs/swagger generates live OpenAPI specs from decorators, keeping documentation synchronized with the actual implementation.

Question 3

A NestJS microservice must guarantee message delivery even if the consumer is temporarily unavailable. What pattern should be applied?

Accepted Answer

Use a message broker with durable queues such as RabbitMQ or Kafka

Answer

Durable message queues persist messages until they are successfully consumed, providing at-least-once delivery guarantees.

Question 4

When writing unit tests for a NestJS service that depends on TypeORM repositories, what is the recommended approach?

Accepted Answer

Use getRepositoryToken() with a mock repository object in the Test module

Answer

Providing mock repositories via getRepositoryToken() isolates the service under test without a real database connection.

Question 5

What does applying the Single Responsibility Principle look like in a NestJS codebase?

Accepted Answer

Controllers handle HTTP concerns, services contain business logic, and repositories manage data access

Answer

Separating HTTP, business, and data-access concerns into distinct layers keeps each class focused and independently testable.

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