Interview Q&A

Short answer: React is a JavaScript library for building user interfaces, mainly for single-page applications. It helps developers create reusable UI components, manage state efficiently, and update the UI in a performant way. ✅ Why use React? Easy to break UIs into components Efficient updates with Virtual DOM Rich ecosystem (React Router, Redux, etc.) Backed by Facebook and a large community

Real-world example (ShopNest)

ShopNest’s storefront is React: components for ProductCard, CartDrawer, and CheckoutForm, with hooks for local UI state.

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: React is a JavaScript library for building user interfaces, mainly for single-page applications. It helps developers create reusable UI components, manage state efficiently, and update the UI in a performant way. ✅ Why use React? Easy to break UIs into components Efficient updates with Virtual DOM Rich ecosystem (React Router, Redux, etc.) Backed by Facebook and a large community

Real-world example (ShopNest)

ShopNest’s storefront is React: components for ProductCard, CartDrawer, and CheckoutForm, with hooks for local UI state.

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: Can browsers read JSX directly? JSX stands for JavaScript XML. It lets you write HTML-like syntax in JavaScript. const element = <h1>Hello, world!</h1>; 🚫 No, browsers cannot read JSX directly. JSX needs to be transpiled (e.g., using Babel) into regular JavaScript.

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: function Home() { return <h1>Home Page</h1>; } function About() { return <h1>About Page</h1>; }

Example code

function Home() { return <h1>Home Page</h1>;
} function About() { return <h1>About Page</h1>;
}

Real-world example (ShopNest)

ShopNest’s storefront is React: components for ProductCard, CartDrawer, and CheckoutForm, with hooks for local UI state.

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: JSX stands for JavaScript XML. It lets you write HTML-like syntax in JavaScript. const element = <h1>Hello, world!</h1>; 🚫 No, browsers cannot read JSX directly. JSX needs to be transpiled (e.g., using Babel) into regular JavaScript. JSX stands for JavaScript XML. It lets you write HTML-like syntax in JavaScript. const element = <h1>Hello, world!</h1>; 🚫…… No, browsers cannot read JSX directly. JSX needs to be…

Explain a bit more

transpiled (e.g., using Babel) into regular JavaScript. JSX stands for JavaScript XML. It lets you write HTML-like syntax in JavaScript. const element = <h1>Hello, world!</h1>; 🚫 No, browsers cannot read JSX directly. JSX needs to be transpiled (e.g., using Babel) into regular JavaScript. JSX stands for JavaScript XML. It lets you write HTML-like syntax in JavaScript. const element = <h1>Hello, world!</h1>; 🚫 No, browsers cannot read JSX directly. JSX needs to be transpiled (e.g., using Babel) into regular JavaScript.

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: React is a JavaScript library for building user interfaces, mainly for single-page applications.

Explain a bit more

It uses standard HTTP methods to perform CRUD operations on resources, which are typically represented as URLs. ✅ A RESTful API allows different systems (like frontend apps or mobile apps) to interact with your server over HTTP in a stateless manner. 📌 Example: GET /users – Get all users POST /users – Create a new user PUT… /users/1 – Update…… user with ID 1 DELETE /users/1 – Delete user with ID 1

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: REST (Representational State Transfer) is an architectural style for designing networked applications.

Explain a bit more

It uses standard HTTP methods to perform CRUD operations on resources, which are typically represented as URLs. ✅ A RESTful API allows different systems (like frontend apps or mobile apps) to interact with your server over HTTP in a stateless manner. 📌 Example: GET /users – Get all users POST /users – Create a new user PUT /users/1 – Update user with ID 1 DELETE /users/1 – Delete user with ID 1

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.js is a fast, minimal, and flexible Node.js web framework. It simplifies building web applications and APIs by handling routing, middleware, requests, responses, and more. ✅ It’s like jQuery for the backend — removes the boilerplate.

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: Applications and APIs by handling routing, middleware, requests, responses, and more. ✅ It’s like jQuery for the backend — removes the boilerplate.

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: An operation is idempotent if repeating it has the same effect as doing it once (e.g., PUT). Important for safe retries.

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.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID: ${id}`); }); Request to /users/42 returns: User ID: 42 pp.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID: ${id}`); }); Request to /users/42 returns: User ID: 42 pp.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID:… ${id}`); }); Request to /users/42 returns: User ID: 42…

Explain a bit more

pp.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID: ${id}`); }); Request to /users/42 returns: User ID: 42

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: Stateless: Each request is independent; no session stored on server. Stateful: Server keeps session info (like login status). Stateless apps scale easier. Testing & Debugging

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: Middleware is a function that runs between the request and response cycle. It can: Modify request/response Execute logic Call the next middleware 📌

Example code

app.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route });

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: pp.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route }); pp.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route }); pp.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route });… pp.use((req, res, next) => { console.log(`${req.method}…

Explain a bit more

${req.url}`); next(); // Move to next middleware or route });

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: Method Purpose app.use () Middleware for all requests app.get () Handle only GET requests 📌

Example code

app.use(authMiddleware); // Runs on all routes app.get('/data', handler); // Runs only for GET /data

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: Write tests before code, then develop just enough to pass tests. Use frameworks like Mocha or Jest.

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 () Middleware for all requests pp.get () Handle only GET requests 📌 pp.use(authMiddleware); // Runs on all routes pp.get('/data', handler); // Runs only for GET /data pp.use () Middleware for all requests pp.get () Handle only GET requests 📌

Example code

pp.use(authMiddleware); // Runs on all routes pp.get('/data',… handler); // Runs only for… pp.use () Middleware for all requests pp.get () Handle only GET requests 📌 Example: pp.use(authMiddleware); // Runs on all routes pp.get('/data', handler); // Runs only for GET /data pp.use () Middleware for all requests pp.get () Handle only GET requests 📌 Example: pp.use(authMiddleware); // Runs on all routes pp.get('/data',… handler); // Runs only for GET /data

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((req, res) => { res.status(404).json({ message: 'Route not found' }); }); pp.use((req, res) => { res.status(404).json({ message: 'Route not found' }); }); pp.use((req, res) => { res.status(404).json({ message: 'Route not found' }); }); pp.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: Node Version Manager lets you install and switch between Node.js versions easily.

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: npm: Default Node package manager. yarn: Faster installs, better caching. pnpm: Efficient disk usage by linking packages.

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: Babel: Transpiles modern JS to compatible versions. TypeScript: Adds static typing and compiles to 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: Rate limiting prevents abuse by limiting the number of requests a user can make in a given time. 📌 Use express-rate-limit: npm install express-rate-limit const rateLimit = require('express-rate-limit'); const limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 100 // limit per IP }); app.use(limiter);

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: Email HR after your manager agrees in principle. Be factual: current notice, requested LWD, business justification (handover complete), and attach transition plan. HR responds to process and risk, not urgency alone.

Step-by-step approach

1. Never cold-email HR without manager alignment—get verbal or Teams approval first.
2. Use official HR ticket/portal if your company has one (TCS/Infosys often require this).
3. Include: employee ID, resignation date, contractual notice, requested LWD, manager name.
4. Attach KT checklist and confirmation that access/assets will be returned on LWD.
5. Ask for response timeline: “Kindly confirm by [date] so I can coordinate with the new employer.”
6. If rejected, request written reason citing policy clause for future reference.

Real-world example

Rahul’s manager agreed on Teams to support 60-day release. Rahul opened an HR ticket with screenshot of project KT completion and manager’s email. HR approved in 3 business days and updated LWD in the separation portal—avoiding confusion at full & final settlement.

What to say / email template

Dear HR Team,

I submitted resignation on [date]. Contractual notice period: 90 days (LWD [date]).

With manager [Name]’s support, I request LWD [new date] based on completed handover (KT doc attached, manager approval email attached).

Please confirm approval or advise additional steps.

Employee ID: ___
Regards, ___

Mistakes to avoid

• Emotional language or comparing yourself to others who “got 15 days.”
• Copying only HR without manager—request gets stuck or rejected.
• Missing attachments—HR will delay for “incomplete submission.”
• Calling HR daily—polite follow-up every 3–5 business days is enough.

Subject line that works: “Notice period reduction request — [Name] — [Emp ID] — Manager approved”

Short answer: Resign in person or video call to your manager first, then submit formal email to HR the same day. Stay positive, give adequate notice, and focus on handover—not grievances. Professional exits protect references and future background checks.

Step-by-step approach

1. Choose timing: avoid peak release week unless unavoidable; give manager heads-up privately.
2. Prepare resignation letter/email before the conversation.
3. Thank manager for growth; state last working day per contract.
4. Ask about handover expectations and exit formalities (assets, access, exit interview).
5. Inform HR via official channel; complete separation portal steps.
6. Remain productive; do not download client data or solicit colleagues to leave.

Real-world example

Neha met her manager on Monday morning, explained she accepted a product role, and shared a 2-week handover outline. She submitted HR resignation by noon, completed exit checklist, and received a positive experience letter mentioning “professional conduct during transition.”

Mistakes to avoid

• Resigning by email without speaking to manager first.
• Using resignation to negotiate salary unless you will genuinely stay.
• Telling teammates before manager—news travels and erodes trust.
• Deleting code or docs out of frustration—can be grounds for legal action.

Toolliyo resources

• Update resume before exit interviews
• More career Q&A

You can be firm and kind: “This was a hard decision; I want to make the transition smooth for the team.”

Short answer: Keep it short: intent to resign, last working day per policy, gratitude, and offer to support handover. Do not include reasons for leaving, complaints, or new employer name unless required.

Step-by-step approach

1. Address manager and HR (or use company resignation template).
2. State: “I hereby resign from my position as [title], effective [resignation date].”
3. Mention contractual notice and proposed LWD.
4. Thank the organization; offer KT support.
5. Sign with full name, employee ID, contact.
6. Attach formal letter PDF if HR requires it.

Real-world example

Arjun sent a 6-line email after a manager call. HR accepted immediately; no back-and-forth because dates matched policy and tone was neutral. His F&F processed on time.

What to say / email template

Subject: Resignation — [Your Full Name] — [Employee ID]

Dear [Manager Name] and HR Team,

Please accept this email as formal notice of my resignation from the position of [Job Title], effective [Resignation Date].

As per my employment terms, my notice period is [X days/weeks], and my expected last working day is [LWD], subject to company policy and handover completion.

I am grateful for the opportunities here and will do my best to ensure a smooth transition, including documentation and knowledge transfer.

Please advise on exit formalities and asset return.

Sincerely,
[Full Name]
[Employee ID]
[Phone]

Mistakes to avoid

• Writing a novel about why you hate the job.
• Naming the new company and salary—creates unnecessary friction.
• Wrong LWD math—HR will ask you to resubmit and delay process.
• Sending from personal email instead of corporate account.

Save a PDF copy—needed for visa, loans, and future verification.