How do you define "Productive"? Aside from that, personally I've used both Akka and plain Scala with Futures, as well as node with Promises, bare callbacks and

How do you define "Productive"? Aside from that, personally I've used both Akka and plain Scala with Futures, as well as node with Promises, bare callbacks and async (though I've not tried fibers). I find Promises and Futures are the perfect balance between simplicity of use and the benefits of using the Async model. There's no need to reason about threads, as they abstract away the actual async implementation, and the interface they expose is very easy to reason about.