The demands and expectations for applications have changed dramatically in recent years. Applications today are deployed on a wide range of infrastructure; from mobile devices up to thousands of nodes running in the cloud—all powered by multi-core processors. They need to be rich and collaborative, have a real-time feel with millisecond response time and should never stop running. Additionally, modern applications are a mashup of external services that need to be consumed and composed to provide the features at hand. We are seeing a new type of applications emerging to address these new challenges—these are being called Reactive Applications. In this talk we will discuss four key traits of Reactive; Event-Driven, Scalable, Resilient and Responsive—how they impact application design, how they interact, their supporting technologies and techniques, how to think when designing and building them—all to make it easier for you and your team to Go Reactive.