The rate limiter that I wrote was a python library to facilite the calling of APIs such that calls were being used as soon as possible given a "cooldown" duration for subsequent API calls. This was used to solve a problem I had encountered where I had access to an API that gave stock ticker information however I had a limit on the amount of calls I could make. The rate limiter allow me to make as many calls as possible in a given amount of time with respect to a limit. Giving me access to data as soon as possible without having to use trivial sleep methods.
The library's source code can be found
here
on my github.