I would have never thought a ruby stack would come anywhere close to Go performance. The path to optimization used to mean abstracting the really crazy parts into a Go microservice for things that just needed absurd responsivity; but it's clear now that a slim ruby stack could also be very effective - and without needing to learn a new language. Worthwhile to at least explore before going Go.
Nor did i know that twitter jumped out of rails before ruby got performant. Which means the argument that twitter outgrew rails isn't so correct anymore.
still, thanks for this insightful comment.