RxJava is an implementation of ReactiveX, the ubiquitus API for dealing with reactive streams. There are much more languages supporting the API, including .NET, Scala and Others.
Combine it with lightweight and modular web frameworks like Jooby, and we may be facing one of the best combos possible nowadays. Add to this recipe a good circuit breaker (Hystrix) and you are good to go. Let’s take a quick look.