Google did not need to write their own SCM to reach the scale mentioned in the article. Off-the-shelf Perforce served that company well enough when it had tens of thousands of engineers and millions of files. They had 11 million files in a monorepo with one 256GB machine which most of you would consider a bare bones desktop computer at this point.

https://www.perforce.com/sites/default/files/still-all-one-s...