Not in my org. Though we did choose it for _one_ new project recently, mostly because we re-used some code from another Django project we had, and we wanted to lean on some readily available functionality from jazzband libs.
We have a few FastAPI services, but are mostly moving away from Python for projects > 1kloc.
next.js + TS for front ends, C# for pure back-end services. Golang was a close second but we have some team experience with C# and like it's lack of ecosystem fragmentation, as that was another gripe we had with Python. The Dapper "micro-orm" is also refreshing after years of struggling to make Django's ORM do the right thing.
The threshold is arbitrary, and likely higher in reality. But we found that we want something with more sound type checking and mypy has lots of rough edges. The Python ecosystem has a lot of catching up to do here.
We have a few FastAPI services, but are mostly moving away from Python for projects > 1kloc.