Reactive applications are the next major evolution of the internet. They allow for applications to be responsive, scalable, and resilient by building on a fully event-driven foundation. However, at the same time, this way of architecting systems introduces some new issues. One of these issues is how to monitor this type of system. This session covers the traditional monitoring approach and different ways to monitor asynchronous applications and finally looks at the way Lightbend has chosen to build a monitoring tool for reactive applications. After this presentation, developers will have a better understanding of how to monitor microservices in a reactive architecture.