Testing, Performance & Deployment
Node.js Interview Questions for Freshers
Node interviews concentrate on the runtime model — the event loop, non-blocking I/O, async patterns — plus Express, REST design, authentication and MongoDB basics.
What is Interview Questions for Freshers in Node.js?
Node interviews concentrate on the runtime model — the event loop, non-blocking I/O, async patterns — plus Express, REST design, authentication and MongoDB basics.
Key points to remember
- Be ready to explain why setTimeout(fn, 0) does not run immediately.
- Expect a practical task: build a small CRUD API with validation and error handling.
- Know how your own project handles authentication and errors.
Frequently asked, with the answer in one line
| Question | Short answer |
|---|---|
| What is Node.js? | A runtime that executes JavaScript outside the browser on the V8 engine. |
| Is Node single-threaded? | Your JavaScript runs on one thread; I/O uses a thread pool and OS async APIs. |
| What is the event loop? | The mechanism that picks up completed async operations and runs their callbacks. |
| What blocks the event loop? | Any long synchronous work — sync file reads, tight loops, large JSON parsing. |
| Callbacks vs promises vs async/await? | Three generations of the same idea; async/await is the readable modern form. |
| What is middleware in Express? | A function receiving (req, res, next) that runs before the route handler. |
| How do you handle errors in Express? | Error middleware with four parameters, registered last. |
| CommonJS vs ES modules? | require/module.exports versus import/export; ESM is the standard. |
| How do you store passwords? | Hashed with bcrypt, argon2 or scrypt and a per-user salt — never plain or SHA. |
| JWT vs sessions? | JWT is stateless and hard to revoke; sessions are server-stored and revocable instantly. |
| How do you scale a Node app? | One process per core with cluster or PM2, plus caching and a load balancer. |
| What is a stream? | An abstraction for processing data in chunks instead of loading it all into memory. |
Node.js Interview Questions for Freshers— Interview Questions & FAQs
What Node.js topics are asked most in fresher interviews?+
The event loop and non-blocking I/O, async/await and promises, Express middleware and routing, REST and status codes, MongoDB CRUD, and authentication with JWT or sessions.
Do I need to know MongoDB for a Node.js job?+
Usually yes — MERN and MEAN stack roles assume it. Knowing SQL as well is a genuine advantage, since many companies run PostgreSQL or MySQL behind their Node services.