Admittedly very few, although I did run into performance issues on Rails sites handling orders of magnitude less traffic. It's an interesting use case though --

Admittedly very few, although I did run into performance issues on Rails sites handling orders of magnitude less traffic. It's an interesting use case though -- tough to imagine a simpler web app than circa-2006 Twitter. Tellingly, they ultimately threw up their hands and moved it all to Scala.