My company has a 50m LOC Python codebase in a monorepo. It works really well, given the rate of change of thousands of developers globally. That is only possible because of the significant investment in devtools, testing and the deployment infrastructure.
Here is "Python at Massive Scale", my talk about it at PyData London earlier this year:
Here is "Python at Massive Scale", my talk about it at PyData London earlier this year:
https://youtu.be/ZYD9yyMh9Hk