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How do you implement rate-limited job processing so a Node.js worker doesn't exceed a downstream third-party API's request limits?

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Answer

Rate limiting at the worker level throttles how many jobs are processed within a given time window (like 'no more than 100 jobs per minute'), independent of the worker's concurrency setting -- most job queue libraries support this natively (BullMQ's 'limiter' option), which is essential when a job's actual work involves calling a third-party API with a strict rate limit, since exceeding it can trigger errors, temporary bans, or increased costs.

const worker = new Worker('sms-notifications', sendSms, {
  connection,
  limiter: {
    max: 100,     // process at most 100 jobs
    duration: 60000, // per 60-second window
  },
});

Real-world example An SMS-notification worker calling a provider with a strict limit of 100 requests per minute configures BullMQ's built-in limiter to match exactly, ensuring the worker automatically throttles itself instead of repeatedly hitting the provider's rate limit and having messages fail or get queued for retry unnecessarily.

Common follow-ups: How does queue-level rate limiting interact with a circuit breaker also wrapping the same downstream call?;What happens to jobs that arrive faster than the configured rate limit allows them to be processed -- do they simply wait in the queue?

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