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Async · medium

28. Promise Concurrency & Pool Patterns

Throttling parallel asynchronous operations.

1 min read3 questionsup to 50 XPtopic 28/50

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Running hundreds of promises simultaneously can overload RPC nodes or exhaustion limits. A concurrency pool bounds active tasks.

js
async function asyncPool(limit, tasks) {
  const executing = new Set();
  for (const task of tasks) {
    const p = Promise.resolve().then(task);
    executing.add(p);
    p.finally(() => executing.delete(p));
    if (executing.size >= limit) await Promise.race(executing);
  }
}

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Check your understanding

  1. 1. Why should you throttle parallel async network calls?

  2. 2. Which method is useful for tracking the first settling promise in a pool?

  3. 3. What does p.finally() guarantee?

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