If you get 100 per second but they take 100s each how can it possibly keep up? Maybe I am misreading that part, but anyway unless it's thousands or millions of requests a second your synchronization code should not be taking long. If it is, you are doing something wrong, possibly locking while you execute the whole job or something.
For multithreaded code, going to an even higher level language is probably a mistake. Even if you write the application part in erlang or whatever the multithreading should probably be in Java or move to C++ if performance really becomes an issue.
