For high performance/throughput, the JVM beats both Go and Node.js. As an anecdote, I implemented a web service that was handling about 6000 requests per second

For high performance/throughput, the JVM beats both Go and Node.js. As an anecdote, I implemented a web service that was handling about 6000 requests per second of real traffic, per EC2 c1.medium server instance. In terms of dealing with concurrency, I/O, reactive stuff and everything else related, you've got: - Actors (local or remote): http://akka.io/ http://akka.io/ - STM: http://nbronson.github.io/scala-stm/ http://nbronson.github.io/scala-stm/ - Futures/Promises in the standard library: http://docs.scala-lang.org/overviews/core/futures.html http://docs.scala-lang.org/overviews/core/futures.html - Async (e.g. C#'s async): https://github.com/scala/async https://github.com/scala/async - RxJava Observables: https://github.com/Netflix/RxJava https://github.com/Netflix/RxJava - Iteratees: http://www.playframework.com/documentation/2.2.1/Iteratees http://www.playframework.com/documentation/2.2.1/Iteratees - Scalaz Streams: https://github.com/scalaz/scalaz-stream https://github.com/scalaz/scalaz-stream And the list can go on.