The Stream API is among the most important API introduced in the JDK 8. New patterns have been introduced, enabling new ways to process data, especially in parallel. The Java 8 Stream API is not alone on this segment. We would like to present here RxJava, a popular API, brought by Netflix. The patterns offered by this API are quite different from the Stream API. This presentation compares those two APIs, from the developer point of view. What patterns are proposed on both sides, and what are the performances of those patterns. Many examples and benchmarks (using JMH) are shown. The goal is not to state which one of those APIs is the best, but merely give keys to decide which one is the best suited for my application.