From the 'it's what all the cool kids use' files:

Like everyone else, I've been a fan of Twitter (but don't call me a Twit) since it debuted over a year ago. In the last week or so Twitter has had a bunch of problems with service disruption and the like - in response Twitter developers are opening up about what makes Twitter run.  A lot of what makes Twitter run is Ruby on Rails (RoR).

We've got a ton of code in Ruby, and we'll continue to develop in Ruby with Rails for our front-end work for some time.  There's plenty to do in our system that Ruby is a great fit for, and other places where different languages and technologies are a better fit.  Our key problems have been primarily architectural and growing our infrastructure to keep up with our growth.

Twitter developers believe in RoR and they've noted that it is the a great tool for development and rapid prototyping.

The problems of scaling are not unique to RoR (or Twitter) and it's a problem that I hope they figure out sooner rather than later. Twitter is a customer of Rails performance management vendor New Relic, so they do have a bit of external help too.

The RoR ecosystem continues to grow, this week at Railsconf there were a few interesting announcements and it will be interesting see how Twitter continues with its RoR usage and evolution.