Backend Software Engineer Interview Questions Pune NI10020
Backend Software Engineer Interview Questions and Answers - Pune (Remote)
Job ID: NI10020
This guide covers commonly asked interview questions for the Backend Software Engineer (Python & Node.js) position in Pune, Maharashtra. It is useful for candidates preparing for backend developer interviews covering system design, coding, databases, APIs, and remote work capabilities.
Top Interview Questions
1. What is the difference between Django and FastAPI, and when would you choose one over the other?
Django is a full-featured opinionated framework suited for rapid development of complex web applications with an ORM, admin panel, and built-in auth. FastAPI is a modern, high-performance framework ideal for building APIs with asynchronous support and automatic OpenAPI documentation. Choose Django for content-heavy or admin-driven projects and FastAPI for high-throughput microservices or async-first API backends.
2. Explain RESTful API design principles and what makes an API well-designed.
A well-designed REST API uses meaningful resource-based URLs, correct HTTP verbs (GET, POST, PUT, DELETE), consistent response formats with appropriate status codes, versioning for backward compatibility, and proper authentication. It should be stateless, use pagination for large datasets, and return descriptive error messages. Documentation with OpenAPI/Swagger is a strong signal of a production-ready API.
3. How do you handle database performance optimisation in a high-traffic backend application?
Start with query analysis using EXPLAIN to identify slow queries. Add appropriate indexes on frequently queried columns. Implement caching with Redis for hot data. Use connection pooling to manage database connections efficiently. Consider database read replicas for read-heavy workloads. Use pagination instead of fetching all records. For write-heavy scenarios consider batching and async processing with a message queue.
4. What are microservices and what are the trade-offs compared to a monolithic architecture?
Microservices decompose an application into small, independently deployable services each owning its domain. Benefits include independent scaling, technology diversity, and fault isolation. Trade-offs include increased operational complexity, network latency between services, distributed data management challenges, and the need for robust service discovery and monitoring. Microservices are justified at scale when team and product complexity demand it.
5. How do you implement authentication and authorisation in a Node.js or Python API?
Use JWT for stateless authentication — issue a signed token on login and verify it on each request via middleware. For role-based authorisation define roles in the token payload and check them in route guards. Use refresh tokens with short-lived access tokens for security. Implement OAuth2 for third-party authentication. Always store passwords hashed with bcrypt and enforce HTTPS to protect tokens in transit.
6. Describe your experience with Docker and how you use it in backend development.
Docker is used to containerise the backend application along with its dependencies into a portable image. This ensures environment consistency across development, staging, and production. In practice you write a Dockerfile defining the runtime, copy source code, install dependencies, and expose ports. Use Docker Compose for local multi-service setups and Kubernetes for production orchestration. This eliminates the classic it works on my machine problem.
7. How do you approach debugging a production issue in a live backend system?
Start by checking application logs and error monitoring tools like Sentry or Datadog for the root cause. Reproduce the issue in a staging environment if possible. Use distributed tracing if the system is microservices-based. Implement a fix with a targeted change rather than a sweeping refactor. Deploy with a canary release and monitor metrics closely. Always write a post-mortem to prevent recurrence.
8. What is your experience with asynchronous programming in Python or Node.js?
In Python use asyncio with async/await for I/O-bound operations, combined with FastAPI or aiohttp. In Node.js the event loop is inherently asynchronous — use Promises, async/await, and avoid blocking the event loop with CPU-intensive synchronous code. For CPU-bound tasks offload to worker threads or separate processes. Message queues like Celery in Python or Bull in Node.js handle background job processing asynchronously.
Tips for the Interview
- Be ready to code a small function or API endpoint live during the technical round — practise on a whiteboard or editor
- Prepare to discuss a production project you built: architecture decisions, challenges faced, and how you resolved them
- Know the time complexity of common data structures and algorithms — backend interviews often include DSA rounds
- Show familiarity with at least one cloud platform and explain how you deployed a project end to end
- Demonstrate clean code practices — interviewers often review GitHub profiles before the interview