Node.js Interview Questions — Backend & MERN Stack Guide

Node.js powers MERN stack portfolios common in Indian campus projects. Interviewers test runtime internals before Express routing and database integration.

Priority topics

• Event loop phases and libuv thread pool
• Streams and backpressure
• Express middleware chain and error handling
• JWT authentication flow
• MongoDB schema design vs PostgreSQL for Node APIs
• Cluster module and horizontal scaling intro

Security checklist

Validate inputs with Zod, rate-limit auth routes, use helmet, never store plaintext passwords, and sanitize NoSQL injection vectors in MongoDB queries.

Capstone advice

Deploy an API with logging, health checks, Docker, and CI pipeline — then rehearse architecture explanation for 5 minutes without slides.

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