Node.js Interview Questions
Master the event loop, streams, microservices, and backend architecture scaling.
IntermediateScenario Based
How do you prevent the Node.js event loop from blocking?
You prevent blocking by avoiding synchronous operations (like `fs.readFileSync`) and offloading heavy CPU tasks to Worker Threads or external services.
Deep Dive
Node.js runs on a single thread. If you execute a massive `while` loop or complex cryptography on that thread, it cannot process any other incoming HTTP requests. To prevent this, you should use asynchronous I/O methods (which offload work to the libuv thread pool) and use Worker Threads (`worker_threads` module) for heavy CPU-bound tasks like image processing or large JSON parsing.
Real World Example: Imagine an endpoint `/upload-video` that converts a video to MP4. If you run the conversion directly in the main thread, all other users will timeout waiting for your server to respond. Instead, you dispatch the conversion to a Worker Thread or an AWS SQS queue, immediately returning a 'Processing...' status to the user.
💡 Interview Tip:Don't just say 'use async/await'. Async/await does not magically make a CPU-intensive task non-blocking. It only helps with I/O tasks. Be sure to mention Worker Threads for CPU tasks.