RxJava is a library for composing asynchronous and event-based programs using observable sequences for the Java VM. It provides APIs for asynchronous programming with observable streams. Reactive Extensions (Rx) is a library that supports reactive programming with observable streams in many languages. Netflix adopted RxJava to address issues with its legacy API and improve performance of its services. RxJava uses Observables to build responsive and resilient applications in a reactive style.