Earlier quoted context omitted.
PyPy work well with CPython modules but the performance is not that great, with CFFI performance is really good in PyPY, HPy project will change this https://hpyproject.org/
Last I checked, Pypy wasn’t compatible with many important packages in the Python ecosystem. As of a couple years ago, there was no trustworthy, supported package for talking to a Postgres database with Pypy because psycopg2 wasn’t supported.
I have run it with pandas+numpy and postgres+timescale without issue for the last year.