Rate Limits

The CMR API enforces a rate limit of 5 requests per second per partner API key, applied globally across all endpoints and all users.

Rate Limit Response

When you exceed the limit, the API returns:

{
  "status": 429,
  "message": "Too many requests",
  "data": null
}

The Retry-After header tells you the minimum number of seconds to wait before retrying.

NOTE

Webhook deliveries from CMR to your server do not count toward your rate limit. Only outbound requests from your server to the CMR API are counted.

Handling 429s

Always read Retry-After and add a small amount of jitter to avoid thundering-herd retries from multiple concurrent workers.

JavaScript

Python

Staying Under the Limit

Batch requests where possible

Some endpoints accept multiple items in a single call. Use them instead of looping single-item endpoints.

Instead of	Use
`POST /domains/available-single` × N	`POST /domains/available` with `domains: [...]`

Use a request queue for bulk operations

Schedule bulk jobs off-peak

Large batch operations — mass user imports, bulk renewals — should run during off-peak hours to avoid competing with real-time user-facing requests.

Next Steps

Errors

Full status code reference and retry strategy for all error types.

Pagination

Avoid bulk pagination loops hitting the 5 req/sec limit.

Webhooks Overview

API structure, async operations, and environment details.

Rate Limit Response#

Handling 429s#

Staying Under the Limit#

Batch requests where possible#

Use a request queue for bulk operations#

Schedule bulk jobs off-peak#

Next Steps#

Rate Limit Response

Handling 429s

Staying Under the Limit

Batch requests where possible

Use a request queue for bulk operations

Schedule bulk jobs off-peak

Next Steps