They also had that big huff about ActiveRecord not supporting more than one database system in a replicated environment. Humorously, someone from outside of the organization supplied a patch a few minutes later.

To make matters more complicated, Twitter publicly abandoned Starling, their Ruby-based message queue, for something written in Scala. People took that to mean they abandoned Ruby and Rails completely.

As far as I know they are still using Rails to generate the HTML pages. If not, it is a recent change.