If you implement the simple request rate limiter - one important part is how to communicate it to the clients. I had 2 cases in the last year where we breached the limit:

1. A free 3rd party api. We had a limit of 500 requests per day (which was not written down), which we didn't pass for a long time. Then we suddenly started to get 403 errors, which immediately led us to think our token was revoked or expired. Only after it started to work at 12:00, did we understand we breached the limit, and for some reason, they decided to throw unauthorized instead of the standard 429.

2. A paid api, that we heavily use. Recently we reached their limit (100 calls/minute), and started to get 429 responses. The good part, is that in the header we got the time when our limit will be reset. This allowed us to implement internal queueing of the request, without noisy errors. We had the 429 ones, we stored the requests, and then we continued at the allowed time until we hit it again. As it's mainly in rare peaks, this solution is perfect for us.

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