Obviously a JVM stack developer is going to know Java. But in this world of polyglot programming, knowing a bit of JavaScript, Ruby and Scala as well is a must. In fact, it might even make you a ...

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.

How did Twitter handle election tweets? Less Ruby, more Java As Twitter continues to tweak Ruby performance, it moves more to JVM on servers.