[suresk]

I'm not necessarily disagreeing with you (static typed languages are going to be faster on the JVM), but JRuby - partially with the help of invokedynamic, added in Java 7 - has come a long way performance-wise since Twitter began their rewrite.

I wonder if they would have done anything different, had JRuby been where it is now?

[spullara]

JRuby, even when using a lot of Java based libraries, doesn't get you the performance boost you need — it is just incremental over Ruby and even then only with some code.