Event Loop & Async interview questions

Phases, microtasks versus macrotasks, blocking the loop, and streams and backpressure.

3 questions in Node.js & TypeScript.

Node.js and TypeScript on the serverA 20-minute read on how the topic fits together, before the questions.Node.js and TypeScript fundamentals57 short answers on one page, for revising rather than studying.

medium2

mediumScenarioConcept

Your Node service has low CPU but latency spikes for every request at the same moment. What is happening?

Node.js event loop blocking happens when synchronous JavaScript, JSON work, crypto, regex or CPU-heavy code occupies the shared thread. The signal is every endpoint slowing together while event loop delay rises.

4 minmid, senior

mediumConcept

Walk me through the phases of the Node event loop.

Node.js event loop phases explain callback ordering across timers, poll, check, nextTick and promise microtasks. Correct answers separate macro-task phases from microtasks instead of memorising one log order.

4 minmid, senior, staff

hard1

hardConceptCoding

A promise rejects and nothing is awaiting it. What does Node do?

An unhandled promise rejection in Node.js means a promise failed before any code observed the error. Treat it as a bug, await or return the promise chain, and make the process-level handler a last-resort alarm.

4 minmid, senior, staff