Unfortunately the cost of developing this solution in C++ would be forbidding for us.
In our case on the pretty much same loop the difference between Ruby and Clojure was 20-30 times. Please note that using Clojure allowed us direct access to Java libraries, so essentially this is Java performance that we've been able to tap into using Clojure.
Nope. Although JRuby is not very efficient in calling Java code, at least it's not as efficient as Clojure is from what I've read.
Another plus for Clojure is that it allows us to easily have a multi-threaded implementation. JRuby allows native threads too, but Clojure make concurrency really easy, while JRuby just wraps Java threads with nothing more, so I would have to use regular locking and stuff.
In our case on the pretty much same loop the difference between Ruby and Clojure was 20-30 times. Please note that using Clojure allowed us direct access to Java libraries, so essentially this is Java performance that we've been able to tap into using Clojure.