How does async/await work in Node.js?

Direct answer

async functions return Promises; await pauses within the function until a Promise settles — syntax sugar over .then; use try/catch for errors; await serial I/O, Promise.all for independent parallel work; never block the event loop with CPU work inside async.

async/await makes Promise chains readable in route handlers and scripts — but each await still yields to the event loop; it does not create new threads.

Why interviewers ask

Pattern	When
await step1(); await step2();	Sequential dependencies
await Promise.all([a(), b()])	Independent parallel I/O
for (const x of items) await fn(x)	Serial per item — safe for rate limits
Promise.allSettled	Batch where partial failure OK
top-level await	ESM scripts — import runners, CLI tools

try/catch — catches rejected await; map to HTTP 4xx/5xx in handlers.
Floating promises — async IIFE without await at call site → unhandled rejection.
Fastify handlers — async (req, reply) => { await service... } — framework catches rejections.

async-await.mjs

async function importTopics(slugs) {
  const results = await Promise.all(
    slugs.map(async (slug) => {
      const topic = await loadTopic(slug);
      await upsertTopic(topic);
      return slug;
    })
  );
  return results;
}

try {
  await importTopics(["javascript-interview-questions", "nodejs-interview-questions"]);
} catch (err) {
  console.error("Import failed:", err.message);
}