Infosys Full Stack with Node.js Interview Questions & Answers
Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About Infosys hiring for Full Stack with Node.js roles
Infosys is an Indian multinational IT services and consulting company offering digital transformation, cloud, application management, testing and data services to global clients. It is known for its Mysuru training campus where new hires go through foundation programmes. In India it recruits for roles such as systems engineer, test engineer, data analyst and data engineer, often through campus and off-campus drives.
For Full Stack with Node.js roles, this Infosys practice set focuses most on Node.js Core and Event Loop (6), Asynchronous JavaScript (6), Express.js Framework (5), Authentication and Security (4). It has 15 easy, 15 medium questions, so you can start easy and work up to the harder ones.
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
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01
Compare Prisma, Sequelize and TypeORM for SQL databases in Node.js.
Prisma uses a schema file to generate a fully typed client and has excellent TypeScript support and migrations, though complex raw SQL needs escape hatches. Sequelize is mature, promise-based and widely used in older JavaScript projects. TypeORM uses decorators and entity classes, familiar to Java and NestJS developers. Drizzle is a newer lightweight, SQL-like typed option. Pick based on TypeScript use and team familiarity.
helmet is middleware that sets secure HTTP response headers. It adds Content-Security-Policy, Strict-Transport-Security, X-Content-Type-Options nosniff, frame protection and removes X-Powered-By, reducing risks like clickjacking, MIME sniffing and some XSS attacks. It is one line, app.use(helmet()), but CSP usually needs tuning so your frontend scripts and assets still load.
03
How do you implement graceful shutdown in a Node.js server?
Because the queries are independent, run them concurrently with Promise.all so total time is close to the slowest query instead of the sum. Check that the database connection pool is large enough to serve them in parallel. Then add indexes for slow queries, cache rarely changing parts in Redis, and use Promise.allSettled if the page can render with some widgets missing.
05
Explain the main HTTP methods and which are idempotent.
GET reads a resource, POST creates or triggers an action, PUT replaces a resource fully, PATCH updates part of it and DELETE removes it. GET, PUT, DELETE, HEAD and OPTIONS are idempotent, meaning repeating the request has the same effect as doing it once. POST and usually PATCH are not, which is why payment APIs use idempotency keys for POST.
06
What is the difference between OAuth 2.0 and OpenID Connect?
OAuth 2.0 is an authorisation framework that issues access tokens for calling APIs; it does not define who the user is. OpenID Connect is an identity layer on top of OAuth 2.0 that adds an ID token, a JWT with user identity claims, and a userinfo endpoint. For social or enterprise single sign-on you use OIDC; for API access delegation you use OAuth scopes.
07
What is the difference between authentication and authorisation?
Authentication verifies who the user is, for example by checking a password, OTP or OAuth login. Authorisation decides what that verified user is allowed to do, such as whether they can delete an order or view admin reports. In an API, authentication failures return 401 and authorisation failures return 403. Both must be enforced on the server, never only in the frontend.
08
How do access tokens and refresh tokens work together?
The access token is short-lived, around 5 to 15 minutes, and sent with each API request. The refresh token is long-lived, stored securely in an HttpOnly cookie, and used only at a refresh endpoint to get a new access token. Rotate refresh tokens on every use and store their hashes server-side, so a stolen or reused token can be detected and the session revoked.
09
What is Node.js and why is it used for backend development?
Node.js is a JavaScript runtime built on the V8 engine that runs JavaScript outside the browser. It uses a single-threaded event loop with non-blocking I/O, so one process can handle thousands of concurrent connections cheaply. It is popular for APIs, real-time apps and microservices because teams can use one language across frontend and backend and reuse a huge npm ecosystem.
10
How do you enable compression and why should you be careful with it?
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.
Buffer represents a fixed-length sequence of raw bytes stored outside the V8 heap. It is used for binary data such as files, images, TCP packets and crypto output. You create one with Buffer.from('text') or Buffer.alloc(size) and convert with toString('utf8' or 'base64'). Buffer.allocUnsafe is faster but may contain old memory, so fill it before use.
12
Why is structured logging important and which libraries are used?
Structured logs are JSON lines with fields like level, timestamp, requestId, userId and message, so tools like ELK, Loki, Datadog or CloudWatch can search and aggregate them. pino is fast and popular, winston is flexible with many transports. Log at correct levels, include a correlation ID per request, and never log passwords, tokens, full card numbers or Aadhaar numbers.
13
When would you choose NestJS or Fastify over Express?
Choose Fastify when raw performance and built-in schema validation matter; it is faster than Express thanks to optimised routing and serialisation. Choose NestJS for large teams that want structure: modules, dependency injection, decorators and first-class TypeScript, similar to Spring or Angular. Express still suits small to medium services and teams that prefer flexibility and a huge middleware ecosystem.
14
Why is using async callbacks inside forEach a common bug?
Array.forEach ignores the promise returned by an async callback, so it does not wait for any iteration and errors are not caught by the outer function. Code after the loop runs before the work is done. Use for...of with await for sequential processing, or map the items to promises and await Promise.all for parallel processing.
15
What metrics would you monitor for a Node.js API in production?
Use the RED method for requests: rate, errors and duration with p50, p95 and p99. Add Node-specific metrics: event loop lag, heap used, garbage collection time and active handles, plus CPU, memory and restarts. Monitor dependencies such as database query time, pool usage and cache hit ratio. Export with prom-client or OpenTelemetry and alert on symptoms users feel.
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.
17
What is the difference between throwing an error and rejecting a promise inside an async function?
Inside an async function they behave the same: throw new Error() causes the returned promise to reject with that error. Outside async functions, a throw inside a plain callback such as setTimeout is not caught by promise handlers and becomes an uncaught exception. Always reject with Error objects, not strings, so you keep a stack trace.
18
What is package.json and what is the difference between dependencies and devDependencies?
package.json describes a project: name, version, scripts, entry point and dependencies. dependencies are packages needed at runtime, such as express or mongoose. devDependencies are only for development and build, such as jest, eslint or nodemon. Running npm ci --omit=dev in production installs only runtime packages, which keeps Docker images smaller and reduces attack surface.
Code coverage measures how much code tests execute: lines, branches, functions and statements, reported by Jest with --coverage or c8. It shows untested areas but not whether assertions are meaningful. Chasing 100 percent leads to brittle tests of trivial code. A practical target is around 70 to 85 percent with strong coverage of business logic, error paths and security checks.
EventEmitter from the events module implements the publish-subscribe pattern. Objects register listeners with on or once and trigger them with emit. Streams, HTTP servers and sockets all extend it. Always handle the 'error' event, because an emitted error without a listener crashes the process. Watch for memory leaks when listeners are added repeatedly; Node warns after 10 listeners by default.
23
What happens if you forget to await a promise inside a try/catch?
If you call an async function without await, the try/catch only covers the synchronous part, so a later rejection escapes it and becomes an unhandled rejection that can crash the process. The function also continues before the work finishes, causing race conditions like responding before data is saved. ESLint rules such as no-floating-promises in TypeScript help catch this.
24
How do you implement filtering and sorting safely from query parameters?
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.
A Promise is an object representing the eventual result of an asynchronous operation. It has three states: pending, fulfilled with a value, or rejected with a reason. Once settled it never changes. You consume it with then, catch and finally, or with await. Promises chain, so returning a value or promise from then passes it to the next step.
27
What is database normalisation and when would you denormalise?
Normalisation organises tables to remove duplicate data and update anomalies, typically up to third normal form, for example keeping customers and orders in separate tables linked by foreign keys. You denormalise for read performance, such as storing a product name on an order line or a precomputed order count on a user, when joins become expensive. Denormalised data must be kept in sync.
28
A teammate uses fs.readFileSync inside an Express route. What is the problem and what would you suggest?
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.
Middleware is a function with the signature (req, res, next) that runs during the request-response cycle. It can read or modify req and res, end the response, or call next() to pass control to the next middleware. Typical uses are parsing JSON, logging, authentication, CORS and rate limiting. Order matters, because middleware runs in the sequence it is registered.
30
A client reports that a large JSON POST request fails with 413 Payload Too Large. What do you do?
express.json() has a default body limit of 100 KB, so bigger payloads are rejected with 413. If the size is legitimate, raise it for that route only, for example express.json({ limit: '2mb' }), and check any proxy limit such as Nginx client_max_body_size. For very large data, switch to file upload to object storage or pagination instead of huge JSON bodies.
Tips to crack the Infosys Full Stack with Node.js interview
Practise pseudocode output questions and puzzle-style reasoning, which commonly appear in Infosys online tests and HackWithInfy style contests.
Revise SQL joins, normalisation and one programming language well enough to write and explain simple programs on paper.
Mention willingness to learn new technologies and relocate, since Infosys emphasises its training programme and flexible project allocation.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; Infosys interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the Infosys Full Stack with Node.js interview?
Candidates usually go through 4 stages: Online assessment (aptitude, reasoning + pseudocode); Coding test; Technical interview; HR round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the Infosys Full Stack with Node.js interview?
This practice set leans on Node.js Core and Event Loop (6), Asynchronous JavaScript (6), Express.js Framework (5), Authentication and Security (4). Revise those first, then practise explaining one or two of your own projects end to end, because most Infosys interviewers ask you to walk through real work.
Are these the exact questions asked at Infosys?
No. These are curated practice questions that match the skills and difficulty usually tested in it services interviews like Infosys's. They are not a leaked or verified list of past questions.
Where does Infosys hire Full Stack with Node.js professionals in India?
Infosys has large teams in Bengaluru, Mysuru, Pune, Hyderabad, Chennai. Openings and locations change often, so check the Infosys careers page and filter by city and experience.
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