# Rate limit

> A rate limit is the maximum number of API requests accepted per second (or minute) per key; above it the API answers 429 with a Retry-After header, and batch endpoints are the way to send volume.

Limits protect the platform and each account from runaway loops. They are expressed per key over a sliding window, signalled by headers that show the remaining budget, and enforced with a 429 status that tells the client when to try again. A well-behaved client honours `Retry-After` and uses batch calls rather than parallel single requests for volume.

Rate limits are about requests, not messages: one batch of a thousand messages counts as one request.

At SMSMeteor: 50 requests per second per key, with `X-RateLimit-Limit`, `X-RateLimit-Remaining` and `Retry-After`; batches accept 1,000 messages per API request.

Related terms: [Batch endpoint](https://smsmeteor.com/glossary/batch-endpoint), [Exponential backoff](https://smsmeteor.com/glossary/exponential-backoff), [Throughput (TPS)](https://smsmeteor.com/glossary/throughput)

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