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100 Node.js Interview Questions and Answers

Web & Backend · 100 questions, each with a full written answer — free, no sign-up.

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Basic 20Intermediate 20Advanced 20Expert 20Guru 20

Basic

  1. What is Node.js and why is it used?
  2. What is the difference between Node.js and traditional web servers like Apache?
  3. What is the Node.js event loop and how does it work?
  4. Can you explain the role of the ’require’ function in Node.js?
  5. What is npm (Node Package Manager) and how do you use it?
  6. How do you create a simple HTTP server in Node.js?
  7. What are some core modules in Node.js, and what are their functions?
  8. How can you read and write files using Node.js?
  9. What are event emitters in Node.js and how do they work?
  10. What is the purpose of the ’exports’ object in Node.js?
  11. How can you handle errors in Node.js applications?
  12. Explain the concept of non-blocking I/O in Node.js and why it is important.?
  13. What are callbacks in Node.js, and how do they help in asynchronous programming?
  14. What is the role of ’process’ object in Node.js?
  15. How can you create a child process in Node.js?
  16. What is the difference between ’setTimeout’, ’setImmediate’, and ’process.nextTick’ in Node.js?
  17. How do you use environment variables in Node.js applications?
  18. Explain the concept of ’middleware’ in a Node.js application.?
  19. How do you use a third-party package in your Node.js application?
  20. What is the difference between ’global’ and ’local’ installations of npm packages?

Intermediate

  1. What is the difference between ’Buffer’ and ’Stream’ in Node.js?
  2. Can you explain the role of ’Promise’ in Node.js, and how it differs from callbacks?
  3. How can you create a RESTful API using Express.js in Node.js?
  4. What are the differences between ’fs.readFile’ and ’fs.createReadStream’ for reading a file in Node.js?
  5. How do you handle unhandled promise rejections in Node.js applications?
  6. What are the advantages and disadvantages of using a microservices architecture in Node.js applications?
  7. Explain the difference between ’app.use’ and ’app.all’ in Express.js.?
  8. How can you use async/await in Node.js for asynchronous programming?
  9. What is the role of ’cluster’ module in Node.js, and why is it used?
  10. How do you manage sessions in Express.js?
  11. Explain how you can handle CORS (Cross-Origin Resource Sharing) in a Node.js application.?
  12. What are some common middleware patterns in Express.js applications?
  13. How do you create a secure connection (HTTPS) in Node.js?
  14. Explain the concept of ’WebSockets’ and how to use them in Node.js applications.?
  15. What is the purpose of ’error-first’ callback pattern in Node.js?
  16. How do you implement authentication and authorization in a Node.js application using Express.js?
  17. Explain the differences between ’spawn’, ’exec’, and ’fork’ methods in the ’child_process’ module of Node.js.?
  18. How can you use caching mechanisms in Node.js applications to improve performance?
  19. How do you create custom events using the ’EventEmitter’ class in Node.js?
  20. What is the difference between ’dependencies’ and ’devDependencies’ in the ’package.json’ file of a Node.js application?

Advanced

  1. What are the best practices for error handling in Node.js applications?
  2. How do you handle logging in a Node.js application, and what are some popular logging libraries?
  3. Explain the concept of ’event-driven’ architecture in Node.js and its advantages.?
  4. How can you use dependency injection in a Node.js application, and what are its benefits?
  5. How do you ensure your Node.js application is scalable and can handle a high volume of requests?
  6. Explain the differences between ’worker_threads’ and ’cluster’ modules in Node.js for handling concurrency.?
  7. How do you monitor the performance and resource usage of a Node.js application in production?
  8. What are some common security vulnerabilities in Node.js applications, and how can they be mitigated?
  9. Explain the concept of ’throttling’ and ’debouncing’ in Node.js applications, and their use cases.?
  10. How do you ensure code quality and maintainability in a Node.js project?
  11. What are some strategies for handling long-running tasks or computationally expensive operations in Node.js?
  12. Explain the differences between ’bluebird’ and native ’Promise’ in Node.js.?
  13. How can you use feature flags in a Node.js application, and what are their benefits?
  14. What is the role of ’package-lock.json’ in a Node.js project, and why is it important?
  15. How can you use Redis or other external data stores for caching and session management in a Node.js application?
  16. What are the differences between using a relational database (e.g., MySQL) and a NoSQL database (e.g., MongoDB) in a Node.js application?
  17. Explain the concept of ’backpressure’ in Node.js streams and how to handle it.?
  18. How do you perform unit testing and integration testing in a Node.js application?
  19. How can you use server-side rendering in a Node.js application, and what are its benefits?
  20. What are some popular tools and frameworks for deploying and managing Node.js applications in production?

Expert

  1. How do you design and implement a highly available and fault-tolerant Node.js application architecture?
  2. Explain the concept of ’Event Sourcing’ and ’CQRS’ in the context of Node.js applications and their benefits.?
  3. What are some advanced techniques for optimizing the performance of a Node.js application?
  4. How do you ensure proper load balancing and request distribution in a Node.js application deployed across multiple instances?
  5. Explain the role of ’domain-driven design’ in developing complex Node.js applications and its benefits.?
  6. How do you use the ’Observer’ and ’Pub/Sub’ design patterns in a Node.js application, and what are their use cases?
  7. What are some strategies for managing and optimizing database connections in a Node.js application?
  8. How do you handle memory leaks in a Node.js application and what are some tools for detecting them?
  9. What are some best practices for implementing continuous integration and continuous deployment (CI/CD) in a Node.js project?
  10. Explain the concept of ’hot code swapping’ in Node.js applications and its advantages.?
  11. How do you ensure secure communication between microservices in a distributed Node.js application?
  12. What are some strategies for handling versioning and backward compatibility in Node.js APIs?
  13. How do you implement rate limiting in a Node.js application to prevent abuse and ensure fair usage?
  14. What are some best practices for managing and distributing secrets and sensitive information in a Node.js application?
  15. Explain the role of ’service workers’ in Node.js applications and their use cases.?
  16. How do you profile and optimize the performance of CPU-bound tasks in a Node.js application?
  17. What are some advanced error handling techniques in Node.js applications, such as circuit breakers and fallback strategies?
  18. How can you use ’WebAssembly’ in a Node.js application, and what are its benefits?
  19. Explain the concept of ’lazy loading’ in Node.js applications and how it can improve performance.?
  20. What are some strategies for handling real-time data processing and streaming in Node.js applications?

Guru

  1. How do you design a Node.js application for extreme scalability, such as handling millions of concurrent connections?
  2. Explain the concept of ’Distributed Tracing’ in the context of Node.js applications and how it can be used for diagnosing performance issues across microservices.?
  3. What are some advanced techniques for implementing zero-downtime deployments in a Node.js application?
  4. How do you design and implement a custom garbage collection strategy for a Node.js application with specific memory management requirements?
  5. Explain the role of ’Lambda Architecture’ in the context of Node.js applications and how it can be used to build highly scalable and fault-tolerant systems.?
  6. What are some strategies for ensuring data consistency and integrity in a Node.js application with distributed data storage?
  7. How can you integrate machine learning models and algorithms into a Node.js application to enhance its capabilities?
  8. Explain the concept of ’Chaos Engineering’ in the context of Node.js applications and its benefits for ensuring system resilience.?
  9. What are some advanced techniques for implementing real-time data analytics and visualization in Node.js applications?
  10. How do you design a Node.js application to be highly modular and extensible, allowing for easy integration of new features and components?
  11. What are some best practices for implementing multi-tenancy in a Node.js application, ensuring proper isolation and resource allocation among tenants?
  12. How can you leverage ’edge computing’ in a Node.js application to improve performance and reduce latency?
  13. What are some advanced techniques for implementing secure data encryption and tokenization in a Node.js application?
  14. Explain the concept of ’sharding’ in the context of Node.js applications and how it can be used to optimize data storage and retrieval.?
  15. How do you design a Node.js application to be resilient against distributed denial of service (DDoS) attacks and other security threats?
  16. What are some strategies for implementing automatic scaling and resource allocation in a Node.js application based on real-time demand and usage patterns?
  17. How can you leverage ’Function as a Service’ (FaaS) platforms like AWS Lambda in the context of Node.js applications to optimize resource usage and cost?
  18. What are some best practices for implementing API gateways and service meshes in a Node.js application to manage inter-service communication and security?
  19. How do you design and implement a custom Node.js runtime environment to meet specific application requirements and constraints?
  20. What are some cutting-edge developments and research topics in the Node.js ecosystem that could shape the future of the platform and its applications?
📕 Buy this interview preparation book: 100 Node.js questions & answers — PDF + EPUB for $5
Reading is step one. Saying it out loud is the interview. Our AI interviewer calls your phone and runs a realistic Node.js interview — then scores it.
📞 Practice Node.js — free 15 min
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