Backend Developer interview questions & mock practice
A Backend Developer interview in 2026 runs across 4 rounds — dsa round, language & runtime, database & api design, system design. Below are the most-asked Backend 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 Backend Developer interview process
APIs, databases, concurrency and system design — the server-side engineering interview across product companies and fintech.
DSA round
Coding problems plus complexity analysis.
Language & runtime
Deep dive on your primary language (Java/Node/Python/Go) and its concurrency model.
Database & API design
Schema design, indexing, transactions and REST/gRPC API design.
System design
Designing scalable, fault-tolerant backend services.
Most-asked Backend Developer interview questions
12 of the questions Backend Developer candidates are asked most often in India. Practise answering each one out loud in your AI mock interview.
- 1. Explain the difference between SQL and NoSQL, and when you'd choose each.
- 2. What is database indexing and how does it speed up queries?
- 3. Explain ACID properties in a database transaction.
- 4. What is the difference between REST and GraphQL?
- 5. How do you handle concurrency and race conditions in your backend?
- 6. What is a deadlock and how do you prevent it?
- 7. Explain caching strategies — write-through, write-back and cache invalidation.
- 8. What is the difference between horizontal and vertical scaling?
- 9. How would you design a rate limiter for an API?
- 10. Explain database normalisation and when you would denormalise.
- 11. What status codes do you return for different API scenarios?
- 12. How do you secure a REST API (auth, tokens, input validation)?
How to prepare for your Backend Developer interview
Master database fundamentals: indexing, transactions, isolation levels, and query optimisation.
Be able to design a clean REST API: resource naming, status codes, pagination, idempotency and versioning.
Understand your language's concurrency model deeply (threads, async I/O, locks, the GIL if Python).
Practice system design: caching, message queues, sharding, replication and how to avoid single points of failure.
Know security basics cold: authentication vs authorisation, JWT, hashing passwords, and preventing SQL injection.
Practise other roles
- Software Engineer
- Frontend Developer
- Full Stack 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
Backend Developer interview — FAQs
What questions are asked in a Backend Developer interview?
Common Backend Developer interview questions include: Explain the difference between SQL and NoSQL, and when you'd choose each. What is database indexing and how does it speed up queries? Explain ACID properties in a database transaction. What is the difference between REST and GraphQL? Interviews usually run across 4 rounds — DSA round, Language & runtime, Database & API design, System design. Practice all of them with instant AI feedback using OnJob's free mock interview.
How many rounds are in a Backend Developer interview?
A typical Backend Developer interview has 4 rounds: DSA round (Coding problems plus complexity analysis.); Language & runtime (Deep dive on your primary language (Java/Node/Python/Go) and its concurrency model.); Database & API design (Schema design, indexing, transactions and REST/gRPC API design.); System design (Designing scalable, fault-tolerant backend services.).
How do I prepare for a Backend Developer interview?
To prepare for a Backend Developer interview: Master database fundamentals: indexing, transactions, isolation levels, and query optimisation. Be able to design a clean REST API: resource naming, status codes, pagination, idempotency and versioning. Understand your language's concurrency model deeply (threads, async I/O, locks, the GIL if Python). 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 Backend Developer role?
Core Backend Developer skills tested in interviews include REST APIs, SQL, System Design, Caching, Concurrency, Microservices, Security. OnJob shows you exactly which of these skills stand between you and a 100% match on every live Backend Developer job.
Is OnJob's Backend 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 Backend Developer interview
Rehearse every Backend 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.
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