>Rails is the only framework that has proven it _can_ scale.
Citation? Seems like a pretty extraordinary claim.
It was mentioned in the OP but: GitHub, Shopify, AirBnb, Stripe
There are enough business of similar scale being powered by J2EE (or whatever you want to call it today), Spring and ASP.NET.
And a well known fruity brand used to have all their online services on Web Objects for several years.
I'm with you on this claim :)
But, for the sake of truth: - AirBnB migrated from Rails to a micro-services architecture (which I think, they regretted doing too early - I read that somewhere I believe) - Stripe never used Rails: they use Ruby (and Sinatra for the Web part - i.e. dashboard).
But it's true that Github and Shopify both use and scaled Rails monoliths. There are showing the way :)
Related to Ruby perf, I still hear folks worried about rails “not being able to scale”. Let me say something controversial (and clearly wrong): Rails is the only framework that has proven it _can_ scale. GitHub, Shopify, AirBnb, Stripe all use rails and have scaled successfully. Very few other frameworks have that track record.
There’s plenty of reasons to not use rails, but scaling issues doesn’t feel like a strong one to me.