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Full Stack with Node.js Interview Questions in Chennai

36 practice questions with answers for Full Stack with Node.js interviews in Chennai.

Full Stack with Node.js jobs in Chennai

Chennai is a long-standing IT-services and SaaS hub along OMR, with strong demand for testing, data and support-engineering roles. Many companies here hire freshers in large batches and train them on the job.

Below are 36 questions that match the mix of service, product and domain employers hiring node.js developers in Chennai.

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01

What is the MongoDB aggregation pipeline? Give an example.

Databases: MongoDB, SQL and RedisMedium
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// Top 5 cities by revenue in the last 30 days const since = new Date(Date.now() - 30 * 864e5); const result = await Order.aggregate([ { $match: { status: 'paid', createdAt: { $gte: since } } }, { $group: { _id: '$city', revenue: { $sum: '$amount' }, orders: { $sum: 1 } } }, { $sort: { revenue: -1 } }, { $limit: 5 } ]); // Each stage transforms documents; put $match early to use indexes.
02

What is a callback and what is callback hell?

Asynchronous JavaScriptEasy
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A callback is a function passed to another function to run when an asynchronous task finishes, following Node's error-first convention (err, data). Callback hell is deeply nested callbacks where each async step depends on the previous one, making code hard to read, handle errors in and maintain. Promises and async/await flatten the nesting and centralise error handling with catch or try/catch.
03

Write a parameterised query with node-postgres to fetch a user's recent orders.

Databases: MongoDB, SQL and RedisEasy
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const { Pool } = require('pg'); const pool = new Pool({ connectionString: process.env.DATABASE_URL, max: 10 }); async function recentOrders(userId, limit = 10) { const { rows } = await pool.query( `SELECT id, amount, status, created_at FROM orders WHERE user_id = $1 ORDER BY created_at DESC LIMIT $2`, [userId, limit] ); return rows; }
04

A security audit finds that users can see other users' orders by changing the order ID in the URL. How do you fix it?

Authentication and SecurityMedium
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This is broken object level authorisation. Every query must be scoped to the authenticated user: Order.findOne({ _id: id, userId: req.user.id }), returning 404 if not found. Put this check in a shared service or middleware so no route can skip it, add tests that try other users' IDs, and consider non-guessable IDs like UUIDs as defence in depth, not as the fix.
05

What are streams in Node.js and what types exist?

Node.js Core and Event LoopEasy
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Streams process data in chunks instead of loading everything into memory. There are four types: Readable (fs.createReadStream, HTTP request), Writable (fs.createWriteStream, HTTP response), Duplex (TCP socket, both read and write) and Transform (zlib gzip, modifies data as it passes). Streams keep memory flat when serving large files, uploading media or processing big CSV logs.
06

How do you enable compression and why should you be careful with it?

Deployment, Scaling and PerformanceMedium
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Use the compression middleware or, better, let Nginx or the CDN compress responses with gzip or Brotli, which reduces JSON payload size by 70 percent or more. Be careful: compressing in Node uses CPU on the event loop, small responses gain little, and already compressed files like images should be skipped. Never compress responses mixing secrets with user input over HTTPS because of BREACH-style attacks.
07

What is an index and how does it improve query performance?

Databases: MongoDB, SQL and RedisEasy
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An index is a data structure, usually a B-tree, that lets the database find rows without scanning the whole table or collection. Indexes speed up reads on filtered, sorted and joined fields but slow down writes and use storage. Create them based on real query patterns, check usage with EXPLAIN or explain('executionStats'), and remove unused ones.
08

What is a REST API and what are its key constraints?

REST API DesignEasy
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REST is an architectural style where resources are identified by URLs and manipulated through standard HTTP methods. Key constraints: client-server separation, statelessness so each request carries all needed information, cacheable responses, uniform interface, layered system and optionally code on demand. In practice it means resource-based URLs, correct methods and status codes, and JSON representations.
09

How would you structure a large Express project?

Express.js FrameworkMedium
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I use a layered structure: routes define endpoints, controllers handle HTTP details, services hold business logic, and repositories or models talk to the database. Add middlewares, validators, config and utils folders, and group by feature, for example modules/orders, once the app grows. This keeps controllers thin, makes services unit-testable and avoids business rules leaking into routes.
10

Describe a time you disagreed with a senior developer on a technical approach.

Express.js FrameworkEasy
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Situation: a senior wanted to store sessions in server memory for a new API. Task: I believed it would break when we scaled to multiple pods. Action: I prepared a short comparison, showed a demo where users were logged out after a restart, and suggested Redis sessions or JWT. Result: we agreed on Redis, and the senior asked me to document the decision for the team.
11

Write a basic GitHub Actions workflow that tests and builds a Node.js app.

Deployment, Scaling and PerformanceMedium
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name: ci on: [push, pull_request] jobs: test: runs-on: ubuntu-latest services: mongo: image: mongo:7 ports: ['27017:27017'] steps: - uses: actions/checkout@v4 - uses: actions/setup-node@v4 with: node-version: 22 cache: npm - run: npm ci - run: npm run lint - run: npm test -- --coverage env: MONGO_URL: mongodb://localhost:27017/test
12

How do you implement real-time features like live order tracking in Node.js?

Deployment, Scaling and PerformanceMedium
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Use WebSockets through Socket.IO or ws, or Server-Sent Events for one-way updates. Clients join a room per order, and when the rider location or status changes, the server emits to that room. With multiple instances, use the Socket.IO Redis adapter so events reach clients on any server, authenticate the socket on connect, and throttle location updates to save bandwidth.
13

How do you implement graceful shutdown in a Node.js server?

Node.js Core and Event LoopMedium
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const server = app.listen(3000); async function shutdown(signal) { console.log(signal, 'received, closing'); server.close(async () => { await db.close(); await redis.quit(); process.exit(0); }); setTimeout(() => process.exit(1), 10000).unref(); } process.on('SIGTERM', shutdown); process.on('SIGINT', shutdown); // Stops new connections, finishes in-flight requests, closes pools.
14

How do you design Express middleware that checks user roles for a route?

Express.js FrameworkMedium
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Create a factory: const authorize = (...roles) => (req, res, next) => roles.includes(req.user?.role) ? next() : res.status(403).json({ error: 'Forbidden' }). Use it after authentication, for example router.delete('/:id', authenticate, authorize('admin'), handler). Keep roles and permissions in config or the database, and for complex rules move to permission-based checks or a policy library.
15

A Mongoose query returns large documents and the API is slow. What optimisations can you apply?

Databases: MongoDB, SQL and RedisMedium
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Use .select() to fetch only needed fields, and .lean() to return plain objects instead of full Mongoose documents, which cuts memory and CPU. Make sure the filter and sort use an index, checked with explain. Paginate results, avoid populating deep references, and cache frequently read data. For large exports, use a cursor with for await instead of loading everything.
16

After adding a new middleware, all routes return 404 or hang. How do you debug it?

Express.js FrameworkMedium
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A hang usually means the middleware never calls next() or sends a response on some path. A 404 often means it was mounted with a wrong path or registered after routes. I check order of app.use calls, add logging at the start and end of the middleware, verify every branch calls next or responds, and check async code passes errors to next.
17

Write a centralised error handler with a custom AppError class.

Express.js FrameworkMedium
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class AppError extends Error { constructor(message, status = 500) { super(message); this.status = status; } } app.use((err, req, res, next) => { const status = err.status || 500; logger.error({ err, path: req.path }); res.status(status).json({ error: status === 500 ? 'Internal server error' : err.message }); }); // In a route: throw new AppError('User not found', 404);
18

Write a Jest unit test for a function that calculates order total with GST.

Testing and DebuggingEasy
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// pricing.js const total = (items, gst = 0.18) => Math.round(items.reduce((s, i) => s + i.price * i.qty, 0) * (1 + gst) * 100) / 100; module.exports = { total }; // pricing.test.js const { total } = require('./pricing'); describe('total', () => { it('adds 18% GST by default', () => { expect(total([{ price: 100, qty: 2 }])).toBe(236); }); it('returns 0 for an empty cart', () => { expect(total([])).toBe(0); }); });
19

How do you handle a situation where you cannot find the root cause of a bug before a deadline?

Testing and DebuggingEasy
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I inform my lead early with what I know, what I have ruled out and the risk. I propose a safe mitigation, such as a feature flag to disable the path or a rollback, and add extra logging to capture more data. In one case this let us release on time with the feature off, and the new logs revealed the cause two days later.
20

What is a JWT and what are its three parts?

Authentication and SecurityEasy
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A JSON Web Token is a compact, signed token used to carry claims between parties. It has three Base64URL parts separated by dots: header (algorithm and type), payload (claims like sub, role, exp) and signature. The signature proves the token was issued by the server and not modified. The payload is only encoded, not encrypted, so never put secrets in it.
21

How do you manage database schema migrations in a Node.js project?

Databases: MongoDB, SQL and RedisMedium
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Use a migration tool such as Prisma Migrate, Knex, Sequelize CLI or TypeORM migrations, and commit migration files to Git. Each migration has up and ideally down steps and runs in CI and before deployment. For zero downtime, use expand and contract: add new columns first, deploy code that writes both, backfill, switch reads, then drop old columns in a later release.
22

What is the N+1 query problem and how do you fix it?

Databases: MongoDB, SQL and RedisMedium
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N+1 happens when you run one query to fetch a list and then one extra query per item, for example loading 100 posts and then each author separately, causing 101 queries. Fix it with joins or eager loading in SQL ORMs like include in Prisma or Sequelize, populate or $lookup in MongoDB, batching with an IN query, or DataLoader in GraphQL.
23

How does the this keyword behave in arrow functions compared to regular functions?

Asynchronous JavaScriptMedium
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A regular function's this depends on how it is called: the object before the dot, undefined in strict mode for plain calls, or whatever bind, call or apply set. Arrow functions do not have their own this; they capture it lexically from the surrounding scope. That makes arrows ideal for callbacks inside class methods, but unsuitable as object methods that need this.
24

Write a retry function with exponential backoff for a flaky API call.

Asynchronous JavaScriptMedium
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async function retry(fn, retries = 3, baseMs = 200) { for (let attempt = 0; ; attempt++) { try { return await fn(); } catch (err) { if (attempt >= retries) throw err; const delay = baseMs * 2 ** attempt + Math.random() * 100; await new Promise((r) => setTimeout(r, delay)); } } } await retry(() => paymentClient.getStatus(id));
25

What is a closure and how is it used in Node.js code?

Asynchronous JavaScriptEasy
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A closure is a function that remembers variables from the scope where it was created, even after that outer function has returned. In Node it is used for middleware factories like rateLimit({ max: 100 }), private counters, memoisation and module-level state. A risk is memory leaks when closures hold large objects longer than needed, for example inside long-lived event listeners.
26

How do you mock a database or external service in Jest?

Testing and DebuggingMedium
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// order.service.test.js jest.mock('../repositories/orderRepo'); const repo = require('../repositories/orderRepo'); const { cancelOrder } = require('../services/order.service'); test('cannot cancel a shipped order', async () => { repo.findById.mockResolvedValue({ id: 1, status: 'shipped' }); await expect(cancelOrder(1)).rejects.toThrow('Cannot cancel'); expect(repo.update).not.toHaveBeenCalled(); }); // For HTTP calls, nock or msw can intercept requests.
27

A teammate uses fs.readFileSync inside an Express route. What is the problem and what would you suggest?

Node.js Core and Event LoopEasy
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Synchronous file calls block the event loop for the whole read, so under load every request queues behind disk I/O and latency spikes. In a route, use fs.promises.readFile with await, or stream the file with fs.createReadStream and pipe it to the response. Sync calls are acceptable only at startup, for example reading a config file once before the server listens.
28

A scheduled job processes orders with setInterval every minute, but sometimes runs overlap and duplicate emails are sent. How do you fix it?

Asynchronous JavaScriptMedium
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setInterval fires regardless of whether the previous async run finished. Use a recursive setTimeout that schedules the next run only after the current one completes, or keep an isRunning flag. If several instances run, use a distributed lock in Redis or a job queue like BullMQ with unique job IDs. Also make email sending idempotent by recording sent message IDs.
29

How do you optimise JSON serialisation for very large API responses?

Deployment, Scaling and PerformanceHard
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Large JSON.stringify calls block the event loop. Reduce payload size with pagination and field selection first. For unavoidable large outputs, stream the response as NDJSON or a streamed JSON array, use schema-based fast serialisers like fast-json-stringify, which Fastify uses, and cache precomputed responses. Offload heavy transformation to worker threads or background jobs that write files to storage.
30

What is a compound index and why does field order matter?

Databases: MongoDB, SQL and RedisMedium
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A compound index covers multiple fields, such as { userId: 1, createdAt: -1 }. It supports queries that use a prefix of the fields, so it helps queries on userId alone or userId plus createdAt, but not createdAt alone. A good rule in MongoDB is ESR: put equality fields first, then sort fields, then range fields, to avoid in-memory sorts.
31

Tell me about a time a database change caused an issue and what you learned.

Databases: MongoDB, SQL and RedisMedium
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Situation: I added a NOT NULL column with a default to a large MySQL table during business hours. Task: the migration locked the table and checkout slowed down. Action: I rolled back, rewrote it as add nullable column, backfill in batches, then add the constraint, and ran it at low traffic after testing on a production-size copy. Result: no downtime, and we added a migration review checklist.
32

How does error-handling middleware work in Express?

Express.js FrameworkMedium
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Error-handling middleware has four parameters (err, req, res, next) and must be registered after all routes. When any middleware calls next(err) or throws in a synchronous handler, Express skips normal middleware and jumps to the error handler. In Express 4, async errors must be passed to next manually or with a wrapper; Express 5 forwards rejected promises automatically.
33

What is the built-in node:test runner and when would you use it over Jest?

Testing and DebuggingMedium
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Node.js ships a stable test runner in the node:test module with describe, it, mocks, coverage and watch mode, run with node --test. It needs no extra dependency and works natively with ES modules, which Jest still handles with extra configuration. Jest or Vitest offer richer snapshot testing, mocking and ecosystem. For small libraries or ESM-first services, node:test is a lightweight choice.
34

Tell me about a time you had to balance speed of delivery with technical quality.

Deployment, Scaling and PerformanceMedium
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Situation: sales needed a partner API in one week for a client launch. Task: deliver fast without creating a mess. Action: I agreed with my manager to ship the core endpoints with validation, auth and tests, and to defer caching and admin tooling, logging them as tickets with dates. Result: the partner went live on time, and we completed the deferred work in the next sprint as planned.
35

Users report seeing stale prices after an update because of caching. How do you solve it?

Databases: MongoDB, SQL and RedisMedium
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Invalidate or update the cache key in the same code path that updates the price, preferably after the database commit. Use reasonable TTLs as a safety net, and version keys if needed. If several services update prices, publish a price-changed event and have consumers delete the cache. For CDN-cached responses, purge the relevant URLs or use short max-age with stale-while-revalidate.
36

What is the difference between process.nextTick and setImmediate?

Node.js Core and Event LoopMedium
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process.nextTick queues a callback to run immediately after the current operation, before the event loop continues to any phase, even before promise microtasks. setImmediate queues a callback for the check phase of the next loop iteration. Overusing nextTick recursively can starve I/O because the loop never moves on, so setImmediate is safer for deferring heavy work.

Companies with offices in Chennai (3)

Product

Freshworks

Full Stack with Node.js interview questions

  • 30 questions
  • 5 rounds

Chennai, Bengaluru, Hyderabad

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Consulting

Thoughtworks

Full Stack with Node.js interview questions

  • 30 questions
  • 5 rounds

Pune, Bengaluru, Chennai +2

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IT services

Infosys

Full Stack with Node.js interview questions

  • 30 questions
  • 4 rounds

Bengaluru, Mysuru, Pune +2

View questions

Frequently asked questions

Which companies hire Full Stack with Node.js professionals in Chennai?

Companies with large offices in Chennai include Freshworks, Thoughtworks, Infosys. Use their company pages below to practise employer-specific sets.

Are Full Stack with Node.js interviews in Chennai different from other cities?

The questions depend more on the company than the city. Chennai's mix of employers decides the style: Many companies here hire freshers in large batches and train them on the job

How do I find Full Stack with Node.js jobs in Chennai?

Shortlist companies with Chennai offices, keep your CV focused on Full Stack with Node.js projects, apply on company career pages and job portals with the Chennai filter, and practise the questions on this page before each interview.

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