API Rate Limits?

I'm using python to pull data from the API (with my API Key) for a website I'm working on. I was considering using threading/queuing to make some steps faster (basically making a bunch of requests quickly), and I wanted to make sure I wasn't violating any rate limits. Prior to using an API Key, I remember running into an issue (after too many consecutive requests, the API just started timing out), but I wasn't sure what limit I broke or if this was just due to not using an API Key. I haven't tried anything crazy using my API key yet, but can try a test (e.g. something like how fast can my desktop pull 1000 post carnage reports or something like that) if it would help. Also, if there's any other information/details that would help answer this rate limit question, please let me know.