Rate Limits

Overview

Caspen applies a single throttle: 60 requests per minute for each API key. The throttle window starts when you make the first request and resets 60 seconds later, at which point the allowance refills to 60 calls.

Current limit

Limit type	Requests	Window	Scope
Standard	60	60 seconds	Per API key

Reset behavior

When you send a request, the counter tracks how many calls you have made in the last 60 seconds. Once a call becomes older than 60 seconds, it no longer counts against the quota. There is no separate daily or monthly limit.

Response headers

Every response includes throttling headers so you can monitor usage:

HTTP/1.1 200 OK
X-RateLimit-Limit: 60
X-RateLimit-Remaining: 1

Header	Description
`X-RateLimit-Limit`	Maximum requests allowed in the rolling window (always 60).
`X-RateLimit-Remaining`	Remaining requests before you hit the limit.
`Retry-After`	Seconds to wait before retrying. Only present when you are limited.
`X-RateLimit-Reset`	Unix timestamp for when the current window resets.

When you exceed the limit

If you send more than 60 requests within 60 seconds, Caspen returns 429 Too Many Requests with a short error body and backoff headers.

HTTP/1.1 429 Too Many Requests
X-RateLimit-Limit: 60
X-RateLimit-Remaining: 0
Retry-After: 32
X-RateLimit-Reset: 1758868775
Content-Type: application/json

{"message":"Too Many Attempts."}

Wait for the number of seconds indicated in Retry-After or until the time reported in X-RateLimit-Reset before sending the next request.

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Overview

Current limit

Reset behavior

Response headers

When you exceed the limit

​Overview

​Current limit

​Reset behavior

​Response headers

​When you exceed the limit

Overview

Current limit

Reset behavior

Response headers

When you exceed the limit