According to this answer from a Twitter employee, they still use Rails: http://www.quora.com/Does-Twitter-still-use-Ruby-on-Rails/answer/John-Adams-2 http://www

According to this answer from a Twitter employee, they still use Rails: http://www.quora.com/Does-Twitter-still-use-Ruby-on-Rails/answer/John-Adams-2 http://www.quora.com/Does-Twitter-still-use-Ruby-on-Rails/an... Besides that: GitHub, Basecamp, Groupon, Shopify, LivingSocial, YellowPages.com (unless they've changed to something else), etc. Scaling Rails is a solved problem.