This post is dead on. I didn’t understand it fully until I went to large companies. Google has reinvented every part of the stack for better or worse. Certainly I think git would be fine but it didn’t exist in its current capacity when they built their own source control.
But when you operate millions of machines it might actually make sense to have a team hacking on a custom jvm or version of llvm or a custom network stack because single digit percentages point perf increases are tens of millions or even hundreds of millions of dollars worth of value
An alternative is that they're lumbering under the weight of all their tech debt, and rather than fix the tech debt, tech companies throw more capacity at it
The standard tech company approach to all problems has been to throw capacity at every problem, from AWS to airBnB to Uber
But when you operate millions of machines it might actually make sense to have a team hacking on a custom jvm or version of llvm or a custom network stack because single digit percentages point perf increases are tens of millions or even hundreds of millions of dollars worth of value