Async Concurrency Handler

Async Concurrency Handler

Prerequisites & Dependencies

• Node.js 18+ (with Builtin Worker Threads) or Go 1.21+
• p-limit or async-mutex for promise pooling (Node), sync.Mutex for Go
• Familiarity with event loop, promises, or goroutine patterns

Execution Steps

1. Identify bottlenecks or uncontrolled parallelism in existing async code
2. Choose a concurrency control strategy: fixed-size promise pool, token bucket, or goroutine worker pool
3. Implement the pattern with proper synchronization (mutexes, semaphores, or p-limit options)
4. Write unit tests that stress-test the concurrency boundary and detect race conditions (using pytest-asyncio/go test -race)
5. Profile latency and throughput, adjust pool size or timeout values for optimal performance

// Promise pool with p-limit (Node.js)
const pLimit = require('p-limit');

async function processItems(items, concurrency = 5) {
  const limit = pLimit(concurrency);
  const promises = items.map(item => limit(() => heavyCompute(item)));
  const results = await Promise.all(promises);
  return results;
}

async function heavyCompute(x) {
  await new Promise(r => setTimeout(r, 50)); // simulate async work
  return x * 2;
}

// Usage: processItems([1,2,3,4,5], 2) -> runs max 2 at a time