Their post-mortem [0] says the bug was in redis-py, so not FastAPI, but it was similarly due to a race condition in AsyncIO. I wonder if tiangolo had some role in fixing it or if that's just a coincidence. I'm guessing this PR [1] contains the fix (or possibly only a partial fix, according to the latest comment there).

[0] https://openai.com/blog/march-20-chatgpt-outage

[1] https://github.com/redis/redis-py/pull/2641