API is returning 429s when the rate-limit has not been reached

There's 2 rate limiters, one of all APIs, then another for Batch APIs.
- The "all API" rate limiter has a limit of 1000 requests per minute per IP address.
- The "batch API" rate limiter has a limit of 250 requests per minute per IP address.

Sometimes we'll get 429 requests before we hit the limit of 1000 requests per minute, even as low as 200 requests/minute across multiple APIs, need to investigate why.