I had hard time using services that have rate limiting

I was working on 4 projects that require doing many requests at the same time to a single service which has rate limited API. None of my projects can communicate with each other so there was no way of knowing that I'm going to hit rate limit threshold...

And then it hit me! I need a service which would solve this problem for me, which would accept many requests execute them one after another and avoid 429 problem.