[cbsmith]

Even on the networking side, you can see from projects like this that you can get what should be enough messaging performance for any NoSQL store out of Java: https://github.com/real-logic/Aeron

Their Java throughput is about 70% of their C++11 throughput, and that's with a pretty synthetic benchmark where there is not any logic behind those messages. Once you add in some real logic there, it gets even thinner.

They aren't doing user space networking, but that actually ought to allow Java to do even better.