I just want to give a public shout out to Wojtek on this blog post. It shows scalability in for an actual scenario at levels that most users won't need (10M req/s!). Beyond that, there is a clear methodology with lots of hard data. This along with listing the work that it took to get there. Very good post!

Disclaimer: I co-founded Kubernetes and help to coordinate the k8s Scalability SIG, although I'm no longer at Google. I didn't see this before it was published, though.