Interview Q&A

Short answer: Use middleware like express-rate-limit to limit the number of requests per IP.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use Express’s built-in middleware: app.use(express.json()); This enables the app to read req.body in JSON POST/PUT requests.

Example code

Use Express’s built-in middleware: app.use(express.json()); This enables the app to read req.body in JSON POST/PUT requests.

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Websockets enable two-way real-time communication over a single TCP connection. Use libraries like socket.io.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.use(express.json()); This enables the app to read req.body in JSON POST/PUT requests. pp.use(express.json()); This enables the app to read req.body in JSON POST/PUT requests. pp.use(express.json()); This enables the app to read req.body in JSON POST/PUT requests. pp.use(express.json()); This enables the app to read req.body in JSON POST/PUT requests.

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: CORS (Cross-Origin Resource Sharing) allows servers to specify who can access their APIs. ✅ Use the cors middleware: npm install cors const cors = require('cors'); app.use(cors()); You can also customize it: app.use(cors({ origin: ' }));

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: PIs. ✅ Use the cors middleware: npm install cors const cors = require('cors'); pp.use(cors()); You can also customize it: pp.use(cors({ origin: ' })); PIs. ✅ Use the cors middleware: npm install cors const cors = require('cors'); pp.use(cors()); You can also customize it: pp.use(cors({ origin: ' })); PIs. ✅ Use the cors middleware: npm install cors const… cors = require('cors'); pp.use(cors()); You can also…

Explain a bit more

customize it: pp.use(cors({ origin: ' })); PIs. ✅ Use the cors middleware: npm install cors const cors = require('cors'); pp.use(cors()); You can also customize it: pp.use(cors({ origin: ' }));

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use console.log for quick checks. Use node --inspect and Chrome DevTools. Use debuggers in IDEs (VSCode). Use profiling tools like clinic.js.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: You define a catch-all middleware after all routes: app.use((req, res) => { res.status(404).json({ message: 'Route not found' }); });

Example code

You define a catch-all middleware after all routes: app.use((req, res) => { res.status(404).json({ message: 'Route not found' }); });

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use libraries like nock to intercept and mock HTTP calls.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use HTTPS Implement authentication & authorization (e.g., JWT) Sanitize inputs to prevent XSS/SQLi Rate-limit requests Use helmet for HTTP headers: const helmet = require('helmet'); app.use(helmet());

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use tools like Apache JMeter, k6, or Artillery to simulate many users and measure performance. Ecosystem & Tools

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: You can use validation libraries to ensure incoming data is valid. 📌 Example with express-validator: npm install express-validator const { body, validationResult } = require('express-validator'); app.post('/users', body('email').isEmail(), (req, res) => { const errors = validationResult(req);

Example code

if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() }); res.send('User created'); });

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.post('/users', body('email').isEmail(), (req, res) => { const errors = validationResult(req); if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() }); res.send('User created'); }); pp.post('/users', body('email').isEmail(), (req, res) => { const errors = validationResult(req); if (!errors.isEmpty())… return res.status(400).json({…… errors: errors.array() }); res.send('User created'); }); pp.

Explain a bit more

post('/users', body('email').isEmail(), (req, res) => { const errors = validationResult(req); if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() }); res.send('User created'); }); pp.post('/users', body('email').isEmail(), (req, res) => { const errors = validationResult(req); if (!errors.isEmpty())… return res.status(400).json({ errors: errors.array() }); res.send('User created'); });

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: express-validator Joi yup zod All support schema-based and custom validations.

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Uses semantic versioning: MAJOR.MINOR.PATCH. New major versions can include breaking changes.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ll support schema-based and custom validations.

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Typical options include: JWT tokens OAuth API keys Sessions (less common for APIs) 📌 Usually, the client includes a token in the Authorization header: Authorization: Bearer <token> The server verifies the token on every request.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: uthorization: Bearer <token> The server verifies the token on every request.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: JWT (JSON Web Token) is a compact, URL-safe token used for securely transmitting information. Consists of Header, Payload, and Signature Used to verify user identity and permissions 📌 Generate: const jwt = require('jsonwebtoken'); const token = jwt.sign({ id: user.id }, 'secret', { expiresIn: '1h' }); 📌 Verify: jwt.verify(token, 'secret');

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use the multer middleware: npm install multer 📌 Example: const multer = require('multer'); const upload = multer({ dest: 'uploads/' }); app.post('/upload', upload.single('file'), (req, res) => { res.send('File uploaded'); });

Example code

Use the multer middleware: npm install multer 📌 Example: const multer = require('multer');
const upload = multer({ dest: 'uploads/' }); app.post('/upload', upload.single('file'), (req, res) => { res.send('File uploaded'); });

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.post('/upload', upload.single('file'), (req, res) => { res.send('File uploaded'); }); pp.post('/upload', upload.single('file'), (req, res) => { res.send('File uploaded'); }); pp.post('/upload', upload.single('file'), (req, res) => { res.send('File uploaded'); }); pp.post('/upload', upload.single('file'), (req, res) => { res.send('File uploaded'); });

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use testing frameworks: Jest or Mocha for unit tests Supertest for HTTP API testing 📌 Example with Supertest: const request = require('supertest'); request(app) .get('/api/users') .expect(200) .then(res => { console.log(res.body); });

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use the morgan middleware: npm install morgan const morgan = require('morgan'); app.use(morgan('dev')); Logs every request with method, status, time, etc.

Example code

Use the morgan middleware: npm install morgan const morgan = require('morgan'); app.use(morgan('dev')); Logs every request with method, status, time, etc.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.use(morgan('dev')); Logs every request with method, status, time, etc. pp.use(morgan('dev')); Logs every request with method, status, time, etc. pp.use(morgan('dev')); Logs every request with method, status, time, etc. pp.use(morgan('dev')); Logs every request with method, status, time, etc.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use plural nouns in endpoints (/users, not /user) Use proper HTTP methods Send meaningful status codes Keep URLs simple and consistent Use pagination for large data Protect with authentication/authorization Use versioning (/api/v1/...) Validate and sanitize all inputs NPM and module-related Node.js interview questions

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.