I like how simple it is, but I didn't like the threading.lock usage in your client because of overhead and bottlenecks.[0] Maybe it's not a problem, but my API doesn't use threading so locking isn't necessary. I prefer to instrument my own API with a Python timing decorator, or similar. I also want to instrument my WakaQ background tasks so having a decorator or context manager would be useful there.

[0] https://stackoverflow.com/a/30115176/1290627

I like your pricing, simplicity, and ease of setup (minus being able to instrument my WakaQ tasks). I'll probably try it out!