If you're interviewing for a Senior Software Developer (Node.js) profile, interviewers will likely ask both conceptual and practical questions about JavaScript and Node.js. Here’s a categorized list of important Node.js interview questions along with advantages of JavaScript and Node.js that you should be prepared for.
1. JavaScript and Node.js Advantages Questions
JavaScript Advantages
✅ Asynchronous & Event-Driven – How does JavaScript handle asynchronous operations?
✅ Single-threaded with Non-blocking I/O – How does the event loop work in JavaScript?
✅ Lightweight & Fast – How does V8 optimize JavaScript performance?
✅ Cross-Platform – How can JavaScript run on different platforms?
Node.js Advantages
✅ Non-blocking I/O & Event-Driven Architecture – How does Node.js handle concurrent requests?
✅ Microservices & API Development – Why is Node.js suitable for building APIs and microservices?
✅ Scalability – How can you scale a Node.js application horizontally and vertically?
✅ Rich Ecosystem (NPM Packages) – How does Node.js leverage npm for rapid development?
✅ Real-time Applications – Why is Node.js a good choice for WebSockets and real-time apps?
✅ Stream-based Processing – How does Node.js handle file streaming efficiently?
2. JavaScript Core Questions
Fundamentals & Advanced Concepts
- Explain event loop, call stack, and task queue in JavaScript.
- What is the difference between var, let, and const?
- Explain shallow copy vs deep copy in JavaScript.
- How does prototype-based inheritance work in JavaScript?
- What are closures and how do they work?
- Explain hoisting in JavaScript.
- What is debouncing and throttling in JavaScript?
Asynchronous JavaScript
- Difference between callback, promises, and async/await.
- How does Promise.all() differ from Promise.race()?
- What happens if you use await in a forEach loop?
- How to handle multiple async operations efficiently?
3. Node.js Core Questions
Architecture & Core Concepts
- Explain how Node.js is single-threaded yet handles multiple requests concurrently.
- What is the difference between process.nextTick() and setImmediate()?
- What is the role of the event loop in Node.js?
- How does Node.js handle child processes?
- Explain the Cluster module and how it helps in scaling.
- What is worker threads in Node.js, and when should you use them?
File System & Streams
- How does fs module work in Node.js?
- Difference between readFile() and createReadStream()?
- How does streaming improve performance in Node.js?
Error Handling
- Difference between try-catch vs process.on('uncaughtException')?
- What is the best way to handle async errors in Node.js?
- Explain how to use domain modules for error handling (deprecated concept)?
Performance Optimization
- How can you increase performance in a high-load Node.js application?
- What are best practices for memory management in Node.js?
- How does Garbage Collection work in Node.js?
- How to debug memory leaks in Node.js?
4. Express.js and Middleware
- What is middleware in Express.js?
- How does Express handle routing?
- Difference between app.use() and app.get()/app.post()?
- How does error-handling middleware work in Express?
- What is CORS, and how do you enable it in Express?
- How does rate limiting work in Express.js?
5. Database & ORM (SQL & NoSQL)
- How does Node.js interact with SQL and NoSQL databases?
- What is the difference between Sequelize, TypeORM, and Mongoose?
- What are database connection pooling and best practices in Node.js?
- Difference between ACID vs BASE in databases?
- How do you prevent SQL injection in Node.js?
6. Security Best Practices
- How do you prevent Cross-Site Scripting (XSS) in Node.js?
- How do you prevent SQL Injection in a Node.js API?
- Explain Cross-Origin Resource Sharing (CORS) and how to configure it.
- What are JWT tokens, and how do they work in authentication?
- How do you handle rate limiting & brute-force attacks in Node.js?
7. Microservices & WebSockets
- How would you design a scalable microservices architecture in Node.js?
- Explain how WebSockets work in Node.js.
- What is the role of Redis in microservices?
- How do you implement message queues (Kafka, RabbitMQ, Redis Pub/Sub)?
8. Caching & Performance
- How does Redis improve performance in Node.js applications?
- What is lazy loading vs eager loading in database queries?
- How does Node.js handle high-throughput applications efficiently?
- Explain caching strategies in Node.js (in-memory, Redis, CDN, etc.).
9. DevOps & CI/CD
- How would you deploy a Node.js application on AWS/Docker/Kubernetes?
- What is the best way to manage environment variables in Node.js?
- How do you handle logging & monitoring in a Node.js application?
- Explain how PM2 helps in process management.
10. System Design Questions
- How would you design a real-time chat application using Node.js?
- How do you scale an API that handles millions of requests per second?
- How would you implement load balancing in a Node.js application?
- How would you design a distributed job queue system?
Bonus: Hands-on Coding Questions
- Implement a custom middleware in Express.js.
- Implement a rate limiter using Redis in Node.js.
- Write a Node.js function to process large files efficiently.
- Implement an **API that caches
Top comments (0)