Unlock Node.js Mastery: Advanced Questions for Senior-Level Interviews

Core Concepts

1. What is the purpose of the Node.js runtime?
2. How does the event loop work in Node.js?
3. Explain the difference between process.nextTick() and setImmediate().
4. What are streams in Node.js, and what are their types?
5. How does Node.js handle asynchronous operations?
6. Explain the concept of non-blocking I/O in Node.js.
7. What is REPL in Node.js?
8. What is the role of libuv in Node.js?
9. How does Node.js manage memory?
10. Explain the differences between CommonJS and ES Modules in Node.js.

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Advanced Concepts

1. What are worker threads, and when should they be used?
2. How does Cluster Module work in Node.js?
3. Explain asynchronous iteration with examples.
4. How does the require() cache work in Node.js?
5. What is event delegation, and how is it implemented in Node.js?
6. Explain Node.js buffering and its role in stream processing.
7. What are the key differences between child processes and worker threads?
8. How does Garbage Collection work in Node.js?
9. What is the purpose of the domain module, and why is it deprecated?
10. Explain global objects in Node.js and their scope.

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Performance Optimization

1. What are best practices for optimizing Node.js applications?
2. How does lazy loading improve performance in Node.js?
3. What is the purpose of heap profiling, and how do you perform it?
4. How can you use Node.js cluster mode for scaling?
5. Explain CPU profiling and tools for analyzing bottlenecks in Node.js.
6. What are tick-based timers, and how can they optimize event handling?
7. How can you monitor and reduce event loop delays?
8. Explain cache strategies in Node.js to improve performance.
9. What is the role of async_hooks in performance monitoring?
10. How do you manage high concurrency in Node.js applications?

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Security

1. What are common security vulnerabilities in Node.js applications?
2. How do you mitigate SQL injection and NoSQL injection in Node.js?
3. What is Cross-Site Scripting (XSS), and how do you prevent it in Node.js?
4. How do you secure environment variables in Node.js applications?
5. What are CSRF attacks, and how can they be mitigated?
6. Explain the role of Helmet.js in securing Node.js applications.
7. How does Node.js handle CORS, and why is it important?
8. What is the purpose of rate limiting in securing APIs?
9. Explain JWT (JSON Web Tokens) and their role in Node.js authentication.
10. What is the best way to implement input validation in Node.js?

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Middleware and Frameworks

1. What are middleware functions in Express.js?
2. How does Koa.js differ from Express.js?
3. What is NestJS, and why is it gaining popularity?
4. How do you create a custom middleware in Express.js?
5. What is the role of middleware stacking in Node.js frameworks?
6. Explain error-handling middleware in Express.js.
7. How does routing work in Express.js?
8. Compare Hapi.js with Express.js in terms of performance and features.
9. What is Micro.js, and when would you use it?
10. How do you optimize performance in Next.js for Node.js applications?

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Databases and ORMs

1. How does Node.js connect to relational databases like MySQL or PostgreSQL?
2. Explain the benefits of using ORMs like Sequelize or TypeORM.
3. What is the difference between Mongoose and Native MongoDB Driver?
4. How do you implement connection pooling in Node.js?
5. Explain transactions in Node.js and how to handle them.
6. What are raw queries, and when should they be used in Node.js?
7. How does Node.js handle database migrations?
8. What is the role of Redis in Node.js applications?
9. How do you monitor and debug database queries in Node.js?
10. What are the pros and cons of using GraphQL over REST APIs in Node.js?

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API Development

1. How do you design a RESTful API in Node.js?
2. What is GraphQL, and how do you implement it in Node.js?
3. How does rate limiting protect APIs from abuse?
4. What are the best practices for API versioning?
5. Explain error handling in RESTful APIs.
6. How does HATEOAS enhance RESTful APIs?
7. What is the role of OpenAPI/Swagger in documenting Node.js APIs?
8. How do you implement pagination in Node.js APIs?
9. Explain authentication and authorization in APIs.
10. How do you manage asynchronous API calls efficiently?

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Ecosystem Tools and Libraries

1. What is PM2, and how does it help manage Node.js applications?
2. Explain the purpose of nodemon.
3. What is the role of dotenv in Node.js?
4. How do you use compression in Node.js?
5. What are some popular logging libraries in Node.js?
6. How does Babel enhance the Node.js ecosystem?
7. What is Socket.IO, and how does it handle real-time communication?
8. Explain the role of Passport.js in authentication.
9. How does JWT work with Node.js?
10. What is the use of multer in Node.js?

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Testing and Debugging

1. What are the best testing frameworks for Node.js?
2. How do you write unit tests in Node.js?
3. What is the role of supertest in API testing?
4. How does Mocha compare to Jest?
5. How do you debug a Node.js application using Chrome DevTools?
6. Explain mocking in testing Node.js applications.
7. How do you test asynchronous code in Node.js?
8. What is code coverage, and how do you measure it?
9. How does the assert module in Node.js work?
10. What is the role of Sinon.js in testing Node.js?

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Real-World Challenges and Scenarios

1. How do you handle memory leaks in Node.js applications?
2. What are the challenges of deploying Node.js in a microservices architecture?
3. How do you implement graceful shutdown in Node.js?
4. What is the role of observability in Node.js applications?
5. How do you handle retry mechanisms for external API calls?
6. What is dynamic throttling, and how is it implemented in Node.js?
7. How do you secure a real-time application built with Node.js?
8. How does Node.js perform in serverless environments?
9. What strategies can be used to reduce cold starts in Node.js applications?
10. How do you manage configurations in large-scale Node.js projects?

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