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What is the purpose of the 'node:timers/promises' module, and how does it simplify working with delays in async code? What is the difference between Promise.all(), Promise.allSettled(), Promise.race(), and Promise.any()? How does async/await relate to Promises under the hood, and what does 'await' actually do to program execution? What is the difference between running async operations sequentially with multiple awaits versus concurrently with Promise.all()? What is util.promisify(), and when would you still need it in modern Node.js? What is the difference between micro tasks and macro tasks in Node.js's event loop, and how does this affect Promise callback ordering? What is an async generator, and how does 'for await...of' let you consume asynchronously produced data? What is the difference between an unhandled promise rejection and an uncaught exception in Node.js, and how does Node handle each by default? What is a common pitfall when using async/await inside Array.prototype.forEach(), and how do you fix it? How would you implement a concurrency-limited task queue in Node.js to process many async tasks without overwhelming a downstream resource?
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How do you implement a retry-with-exponential-backoff pattern for a flaky async operation in Node.js?

Intermediate

Answer

Exponential backoff retries a failed operation with progressively longer delays between attempts (typically doubling each time, often with added random 'jitter' to avoid multiple clients retrying in lockstep) rather than retrying immediately or at a fixed interval, reducing load on an already-struggling downstream service while still recovering automatically once it becomes available again.
async function retryWithBackoff(fn, maxRetries = 5, baseDelay = 200) {
  for (let attempt = 0; attempt < maxRetries; attempt++) {
    try {
      return await fn();
    } catch (err) {
      if (attempt === maxRetries - 1) throw err;
      const delay = baseDelay * 2 ** attempt + Math.random() * 100;
      await new Promise(resolve => setTimeout(resolve, delay));
    }
  }
}
Real-world example A payment-service client wraps its API calls in a retryWithBackoff helper so that transient network blips or brief rate-limiting from the payment provider are automatically retried up to five times with increasing delays, rather than immediately failing the customer's checkout on the very first transient error.

Common follow-ups: Which types of errors should actually be retried versus failed immediately (like a 400 Bad Request versus a 503 Service Unavailable)?;How does adding jitter specifically help prevent a 'thundering herd' problem?

Error Handling;Cloud & DevOps
All 15 Async Patterns questions