Re: They want performance but they wrote it in Java?
At crazy levels of concurrency, Java can actually have an advantage. C++ has to pay a penalty for maintaining wrappers or shared reference counters when temporary objects are given to multiple threads. At some point the GC pauses in Java add up to less time. In the case of data servers, high concurrency caches are absolutely trivial to write in Java because because expunged elements live exactly as long as needed to satisfy all threads using it.
Of course, Java has the flexibility to suck too. Write Java that looks like C++ and it runs like C++. Add frameworks to give it scripted language features and it runs as slow as a scripted language. The latter style is quite trendy.