# Interview Questions — NestJS: Building Scalable Node.js APIs

Source: https://www.skillbyai.com/en/nestjs/nestjs-interview-questions

> Prepare for NestJS interviews on dependency injection, guards vs pipes vs interceptors, N+1 queries and architecture.

## Core concepts Q&A

Explain: dependency injection, how modules work, the difference between providers and services, guard vs pipe vs interceptor, how middleware fits in.

## Database & performance Q&A

Discuss: N+1 problem and solutions, lazy vs eager loading, migration strategy, caching trade-offs, query optimization.

## Architecture Q&A

How would you structure a large app? Testing strategy? Authentication & authorization? Scaling considerations?