Node.js

Node.js interviews test server-side JavaScript runtime knowledge—not browser DOM APIs. Interviewers expect you to explain how work is scheduled, how modules load, how requests flow through a service, and how performance and security show up in production.

Child sections: Node runtime (event loop, libuv, streams, buffers, timers, workers, cluster), modules and packages, backend fundamentals, Node performance, and Node security.

On interviews: connect JavaScript semantics to the host runtime—what runs on the main thread, what moves to libuv or worker threads, and where validation and secrets belong.

Common pitfalls: calling Node multi-threaded without nuance, ignoring backpressure on streams, and treating npm dependencies as free of operational risk.

The trade-off is balancing simplicity, performance, safety, and operability — name which axis you optimized and what cost you accepted.

Checklist:

• Explain event-loop scheduling and blocking work.
• Trace module resolution and package boundaries.
• Walk a request through middleware and shutdown.
• Classify CPU vs I/O bottlenecks and secure defaults.