Explore the principles and applications of Reactive Streams in this conference talk from Philly ETE 2014. Delve into the evolution of Observers and Observables, learning how back-pressure handling enables distributed stream processing across large-scale clusters. Discover the collaborative effort behind defining common interfaces for interoperable stream implementations on the JVM, involving major tech companies. Gain insights into the design principles and see practical examples using the actor-based implementation in Akka. Cover topics such as the four reactive traits, async boundaries, explicit demand flow control, and the distinctions between streams and collections. Examine code examples in Java 8, Rx Java, and Akka, including basic and advanced scenarios, TCP echo servers, and HTTP sketches.