[hideo]

> If you've worked on a large Python or JS codebase, what was it like to work in?

Rife with footguns.

Things broke all the time until we eventually re-added some form of static type checking.

> How did you make small refactors for example?

We'd write tests first to validate that _wrapped_ large chunks of functionality, commit those, then refactor. The key was to write these tests even if the existing code already had "unit tests" because we often found issues this way.