Node.js Developer Technical Questions Interview Questions
10 curated questions with evaluation guidance for hiring managers.
Explain the Node.js event loop. What are the different phases and what runs in each?
Should explain timers, pending callbacks, idle/prepare, poll, check, close callbacks phases. Should understand process.nextTick and Promise microtask priority. Look for deep event loop understanding.
How do you handle CPU-intensive tasks in Node.js without blocking the event loop?
Should discuss worker threads, child processes, offloading to services, or breaking work into chunks with setImmediate. Look for understanding of Node.js's single-threaded limitation.
Explain the difference between CommonJS and ES Modules in Node.js. What challenges arise when mixing them?
Should discuss require vs. import, synchronous vs. asynchronous loading, strict mode, __dirname absence in ESM, and interoperability caveats. Look for practical migration experience.
How do you implement authentication and authorization in a Node.js application?
Should discuss JWT implementation, refresh token strategy, middleware for auth, role-based access control, and security considerations (token storage, CSRF, session management).
What are Node.js streams? Explain different stream types and a practical use case.
Should explain Readable, Writable, Transform, and Duplex streams, backpressure handling, and piping. Look for practical examples like file processing, HTTP request/response, or data transformation.
How do you manage environment-specific configurations in Node.js?
Should discuss environment variables, dotenv, config validation (Joi, Zod), never committing secrets, and structuring configs for different environments. Look for security awareness.
Describe your approach to error handling in an Express or NestJS application.
Should discuss async error handling, global error middleware, custom error classes, logging, and graceful shutdown. Look for production-grade error handling patterns.
How do you debug a memory leak in a Node.js application?
Should mention heap snapshots (Chrome DevTools), heapdump, clinic.js, monitoring tools, and common causes (event listeners, closures, global variables). Look for systematic debugging approach.
What is the cluster module in Node.js? How does it help with scaling?
Should explain fork workers, load distribution, IPC communication, and zero-downtime restarts using cluster or PM2. Look for understanding of multi-core utilization.
How do you design a REST API in Node.js for high traffic? What performance optimizations do you apply?
Should discuss connection pooling, caching, compression, pagination, async operations, and profiling with tools like autocannon. Look for end-to-end performance thinking.
Want AI-generated interview questions tailored to your specific job description? Workro analyses your JD and generates behavioural and technical questions calibrated for the role, seniority level, and required skills — in seconds.
Try free