I wouldn't rely on Google to learn good practices for technical documentation (unless they want to release their complete internal technical documents on how their recommendation algorithms work, that is).

Instead, check out a reliable open source project like SQLITE, they have great documentation:

https://www.sqlite.org/arch.html

https://github.com/sqlite/sqlite

See previous discussion of sqlite structure here:

https://news.ycombinator.com/item?id=32250426