When a program must process many concurrent data streams, there is a number of general techniques available: for example you may use push or pull, and you may choose to use blocking threads or go asynchronous. In this talk we explore the design space and highlight a number of possible desirable properties of streaming systems. We show where the approach standardized in the Reactive Streams initiative falls in this spectrum, and look at a practical example using Akka Streams on the JVM.