Node.js Handwritten Notes for Placements (Free PDF)

Backend interviews for MERN and Node.js roles test two things: whether you understand how Node actually runs your code, and whether you can build an API that is correct, secure and fast. These notes cover both, one topic per page.

What makes these Node.js notes different?

• The event loop, properly. Why Node is single-threaded yet fast, what the libuv thread pool does, and the exact order of nextTick, promises, timers and setImmediate.
• Express the way it's used at work. Middleware chains, a central error handler, REST conventions, JWT auth with bcrypt and httpOnly cookies, and a security checklist.
• Scaling questions answered. Cluster vs worker threads, stateless servers with Redis, queues, caching and the N+1 query trap.
• Hinglish where it helps. Streams, middleware and the thread pool each get a short Hinglish explanation next to the English definition.

How should you use these Node.js notes?

Run each snippet with node file.js and guess the output before you look at the answer. Build a small Express API alongside the Express pages. The last page is a one-page cheat sheet for the night before the interview.

This is Part 4 of the series. Pair it with the React handwritten notes for the full MERN stack, and the JavaScript handwritten notes for the language basics.