Java vs. RoR

Twitter survives election after Ruby-to-Java move → 

Twitter first began stepping away from Ruby in 2008, when the company's Ruby-based message queuing system "hit a wall," in the words of former Twitter developer Alex Payne.

"There's a lot of things that Ruby is great at," Payne said at the time, "but long running processes? Particularly memory intensive ones? Not so much."

Twitter's solution was to migrate some of its Ruby code to a new server stack running on the JVM. Initially, the company's development team avoided stock Java in favor of Scala, an alternative JVM language that combines aspects of object-oriented and functional programming. Today, Twitter's software is built from a mix of Scala and ordinary Java code.

A few Twitter services still run on Ruby, too, but according to Rawashdeh these are used increasingly less often. Notably, he says Twitter has now reconfigured its system so that traffic from mobile devices never touches any Ruby-based software at all.