DESCRIPTION  Modern distributed applications must deliver near-realtime performance while simultaneously managing big data and high user loads spread across environments ranging from cloud systems to mobile devices. Unlike traditional enterprise applications which focus on decoupling their internal components by defining programming interfaces, reactive applications go one step further and decouple their components also at runtime. This makes it possible to react effectively and efficiently to failures, varying user demands, and changes in the application's execution environment. The resulting systems are highly concurrent and fault-tolerant, with minimal dependencies among individual system components.     Reactive Design Patterns is a clearly-written guide for building message-driven distributed systems that are resilient, responsive, and elastic. It contains patterns for messaging, flow control, resource management, and concurrency, along with practical issues like test-friendly designs. All patterns include concrete examples using Scala and Akka—in some cases, Java, JavaScript, and Erlang. Software engineers and architects will learn patterns that address day-to-day distributed development problems in a fault-tolerant and scalable way. Project leaders and CTOs will gain a deeper understanding of the reactive design philosophy.       KEY FEATURES  Offers best patterns for building reactive applications All patterns include concrete examples Discover best practices Explains theory behind reactive system design principles   AUDIENCE Readers should be familiar with a standard programming language like Java, C++ or C# and be comfortable with the basics of distributed systems. Although most of the book's examples use the Scala language, no prior experience with Scala or Akka is required.     ABOUT THE TECHNOLOGY The design patterns in this book were collected by the consultants and engineers of Typesafe during thousands of hours spent building enterprise-quality applications using Scala and Akka. Although many reactive patterns can be implemented using standard development tools like Java, others require the capabilities offered by a functional programming language like Scala and an Actor-based concurrency system like Akka.