Node.js interview questions and answers

Timers run setTimeout callbacks, then pending callbacks, idle/prepare, poll for I/O, check for setImmediate, and close callbacks.

Backpressure is the signal that a writable destination is slower than the readable source.

Global caches without bounds, event listeners that are never removed, and closures holding large request objects are common causes.

Worker threads share memory and suit CPU-heavy tasks such as image processing inside one process.

An unhandled promise rejection means async work failed with no catch.

Routes only parse HTTP, controllers map requests to use cases, services hold business rules, and a data layer talks to Mongoose.

On SIGTERM stop accepting new connections, finish in-flight requests, close the HTTP server, then close MongoDB and Redis.

A proxy timeout stops hung clients from holding sockets forever.

Attackers can upload huge files, unexpected MIME types, or stored XSS in SVG.

Generate or accept a request id, put it on logs, and return it on error responses.

Listen for process warnings, ensure every async path catches, and crash responsibly in production supervisors.