You should look at node, its back end javascript and its popularity is booming.
How well does node scale? It's running in one thread, and from my use (a very small amount of experimentation and reading), it doesn't look like it could handle more than a few hundred concurrent users without stringing together some more robust queuing outside of the node code.
Some of the services I've built in Node.js handle 1000 req/s fine without the need for multiple instances or threads.