Hmm,
The user interface runs on Ruby on Rails, which is "fine for people clicking around Web pages," he says. But by the end of the year, Twitter hopes to have a set of services in the back end that are written entirely in Scala.
So they cannot be sure how it will turn out yet
. But if their problems were with scalability, then I believe they can succeed with Scala, because threading in Ruby is not very good.
This article misses one point mentioned in many blogs. They needed to introduce type system in application. And that might mean they used Ruby incorrectly as they thrown away the Ruby's strongest point.
I have checked out Lift before and I have to confess I do not understand it. It is completely reverted logic. But I would like study it later if time allows.
