Full Stack Developer interview questions & mock practice
A Full Stack Developer interview in 2026 runs across 4 rounds — frontend round, backend round, full-stack machine coding, system design & deployment. Below are the most-asked Full Stack Developer interview questions and a focused prep plan. Rehearse every answer with OnJob's free AI mock interview and get instant, specific feedback before the real one.
The Full Stack Developer interview process
End-to-end web engineering — frontend, backend, databases and deployment — for startups and product teams that want one engineer to own a feature.
Frontend round
JavaScript, React and UI fundamentals.
Backend round
API design, databases and server-side logic.
Full-stack machine coding
Build a small end-to-end feature (form → API → DB).
System design & deployment
Architecture, hosting, CI/CD and trade-offs.
Most-asked Full Stack Developer interview questions
12 of the questions Full Stack Developer candidates are asked most often in India. Practise answering each one out loud in your AI mock interview.
- 1. Walk me through what happens from a user clicking a button to data being saved in the database.
- 2. How do you handle authentication and sessions in a full-stack app (JWT vs cookies)?
- 3. Explain CORS and how you fix a CORS error.
- 4. How do you structure a REST API for a CRUD application?
- 5. What is the difference between client-side and server-side rendering?
- 6. How do you prevent SQL injection and XSS in your app?
- 7. Explain state management on the frontend — when do you reach for a library?
- 8. How would you optimise a slow-loading web page end to end?
- 9. What is the difference between SQL and NoSQL, and when would you pick each for a project?
- 10. How do you handle environment variables and secrets across environments?
- 11. Describe your deployment pipeline from commit to production.
- 12. Tell me about a full-stack feature you built end to end.
How to prepare for your Full Stack Developer interview
Be genuinely comfortable on both sides — interviewers probe the half they suspect you're weaker on.
Practice one end-to-end machine-coding task: a form that hits an API and persists to a database, with validation.
Know the request lifecycle cold: browser → DNS → server → DB → response → render.
Understand auth thoroughly: JWT vs sessions, refresh tokens, password hashing and CORS.
Have a deployable side project on GitHub you can walk through, including CI/CD and hosting choices.
Practise other roles
- Software Engineer
- Frontend Developer
- Backend Developer
- Data Analyst
- Data Scientist
- Product Manager
- DevOps Engineer
- Java Developer
- Python Developer
- UI/UX Designer
- Sales / Business Development
- Digital Marketing
- HR / Recruiter
- Accountant
- Customer Support
- Data Engineer
- Machine Learning Engineer
- QA / Test Engineer
- Android Developer
- iOS Developer
- Business Analyst
- Project Manager
- Scrum Master
- SQL Developer
- React Developer
- Node.js Developer
- Cloud Engineer (AWS)
- Cybersecurity Analyst
- Network Engineer
- Database Administrator
- SEO Specialist
- Content Writer
- Graphic Designer
- Sales Executive
- Business Development Manager
- Operations Manager
- Financial Analyst
- Chartered Accountant
- Customer Success Manager
- Technical Support Engineer
- Civil Engineer
Full Stack Developer interview — FAQs
What questions are asked in a Full Stack Developer interview?
Common Full Stack Developer interview questions include: Walk me through what happens from a user clicking a button to data being saved in the database. How do you handle authentication and sessions in a full-stack app (JWT vs cookies)? Explain CORS and how you fix a CORS error. How do you structure a REST API for a CRUD application? Interviews usually run across 4 rounds — Frontend round, Backend round, Full-stack machine coding, System design & deployment. Practice all of them with instant AI feedback using OnJob's free mock interview.
How many rounds are in a Full Stack Developer interview?
A typical Full Stack Developer interview has 4 rounds: Frontend round (JavaScript, React and UI fundamentals.); Backend round (API design, databases and server-side logic.); Full-stack machine coding (Build a small end-to-end feature (form → API → DB).); System design & deployment (Architecture, hosting, CI/CD and trade-offs.).
How do I prepare for a Full Stack Developer interview?
To prepare for a Full Stack Developer interview: Be genuinely comfortable on both sides — interviewers probe the half they suspect you're weaker on. Practice one end-to-end machine-coding task: a form that hits an API and persists to a database, with validation. Know the request lifecycle cold: browser → DNS → server → DB → response → render. Then run a full AI mock interview on OnJob to rehearse out loud and get instant, specific feedback before the real thing.
What skills do I need for a Full Stack Developer role?
Core Full Stack Developer skills tested in interviews include JavaScript, React, Node.js, SQL, REST APIs, Git, Deployment. OnJob shows you exactly which of these skills stand between you and a 100% match on every live Full Stack Developer job.
Is OnJob's Full Stack Developer mock interview free?
Yes. OnJob's AI mock interview is free to start (₹0) and gives you instant feedback on your answers. Pro (₹99/month) adds unlimited interview-prep AI alongside recruiter tracking and unlimited applications.
Ace your Full Stack Developer interview
Rehearse every Full Stack Developer question out loud with OnJob's AI mock interview and get instant, specific feedback. Then apply to AI-matched jobs in one click — free to start.
Everything about Full Stack Developer on OnJob
Move across the whole Full Stack Developer topic — live openings, real salary data, the job description, interview prep, and early-career routes — all in one place.