[vidarh]

It was also never the problem with Twitter. As much as I detest Rails, Rails was used as an excuse for having picked an architecture that did not prepare them for the need to have a properly scalable backend.

Nothing in Rails prevented them from doing that properly, though Rails defaults may well have encouraged them to pick the easy way out initially (that in itself would not have been a problem either, if they'd started work on a proper backend in the background).

Sharded large-scale delivery of messages has been a "solved" problem for decades, irrespective of language. Twitter as-it-is now is big enough to have all kinds of fun operational issues, but when they were struggling their volume was nothing impressive.