Full-Stack Engineer Interview Questions India 2026: Complete Guide (React, Node.js, Databases)

Full-stack interview question categories: (1) React and frontend depth ('Explain the React reconciliation algorithm and how keys affect reconciliation', 'What is the difference between useMemo and useCallback?', 'Explain how React 18 concurrent features: Suspense, useTransition, and useDeferredValue work and when to use them'). (2) Node.js and backend ('Explain the Node.js event loop: what is the difference between the microtask queue and the macrotask queue?', 'How do you implement request rate limiting in Express.js without a Redis dependency?'). (3) Database design ('Design the PostgreSQL schema for a multi-tenant SaaS application with row-level security; write the RLS policy that ensures tenants can only read their own data'). (4) API design and authentication ('Design a JWT-based authentication system; how do you handle token refresh securely?', 'What is the difference between session-based and token-based authentication and when would you use each?'). (5) Full-stack system design ('Design a real-time collaborative document editor: how do you handle concurrent edits, conflict resolution, and live cursor sharing?').

Full-stack architecture topics: (1) Frontend performance (Core Web Vitals: LCP optimisation via image lazy loading and SSR; CLS prevention; TTI reduction via code splitting and React.lazy; bundle size analysis with webpack-bundle-analyzer). (2) Backend-for-frontend (BFF) pattern (a dedicated backend layer that aggregates multiple microservice calls for a specific frontend client: reduces the number of requests the client makes and keeps the frontend decoupled from the microservice architecture). (3) API design patterns (REST vs GraphQL vs tRPC for different use cases; when to use WebSockets for real-time features vs polling vs Server-Sent Events). (4) Database interaction patterns (N+1 query problem in ORMs and how to fix it using eager loading or DataLoader; database connection pooling in Node.js; read replicas for analytics queries). (5) Full-stack observability (distributed tracing across frontend and backend using OpenTelemetry; logging correlation IDs from the browser request through to the database query).

Full-stack roles at Indian startups vs large product companies: Startups (Series A-C): the role is genuinely full-stack. You own features end-to-end from the React component to the database migration, including API design, authentication, and deployment. This is the fastest way to learn the full product lifecycle. The trade-off: no specialisation depth, context-switching is high, and architectural standards vary widely. Large product companies (Swiggy, Razorpay, Flipkart): the 'full-stack' role is often frontend-heavy with backend access (you write React components, design the API contract, and write the backend handler) but core infrastructure (database schema changes, distributed systems) is handled by dedicated backend or platform teams. The interview for a large company full-stack role may be weighted more toward React and frontend performance than pure backend distributed systems depth. Recommendation: if you want depth in either frontend or backend, target large companies for mentorship and tooling. If you want breadth and ownership, target early-stage startups.

Full-stack engineer salary ranges: junior (0-2 years): Rs 7-20 LPA. Mid-level (2-5 years): Rs 18-50 LPA. Senior (5-8 years): Rs 40-90 LPA. Staff and Principal (8+ years): Rs 80-155 LPA. Full-stack engineers earn slightly less than pure backend engineers and slightly more than pure frontend engineers at equivalent levels. Top-paying full-stack employers: Razorpay (Rs 28-75 LPA mid-senior), CRED (Rs 30-80 LPA), Groww (Rs 22-60 LPA), and fintech startups (Series B and above) that need engineers who own features end-to-end. Companies building B2B SaaS products (CleverTap, WebEngage, MoEngage) also have strong demand for full-stack engineers who can own a feature's entire technical stack.