Modern distributed applications run in environments that may include thousands of processors, web and mobile clients, hybrid cloud deployments, and petabytes of data. The traditional patterns and practices for enterprise application development simply can't deliver the millisecond response times and near-perfect reliability these systems require. Reactive applications meet these demands by employing a loosely-coupled system of independent, isolated components that communicate via asynchronous message passing. These systems are highly responsive to changes in load, extremely fault tolerant through self-healing, and designed to elastically scale. For developers working in JVM-based systems, the Typesafe stack, anchored by the Java and Scala programming languages and the Akka toolkit and runtime, gives developers the tools to build a production-ready reactive application platform.