[singron]

Particularly at Google, programming languages, code styles, common libraries, and tools are incredibly similar between teams. There are really low barriers to jumping into someone else's codebase. It's not uncommon to review changes to your team's codebase from people you have never met (on average, maybe weekly?).

Anecdotally I also think a lot of code was generally really well documented. There is some effort to document things for a general Googler audience (i.e. you should understand most of the documentation on any given page without having to read all the other docs).

All in all, once you have onboarded into the Google ecosystem, it's fairly painless to jump around the codebase.