Our applications often interact with external systems. In many cases, we need a persistent connection to one or more of these external services. For example, if your application makes continuous use of a database, you���ll likely want to stay connected to such database so that you can avoid spending time and resources connecting and disconnecting each time you perform a request. With Erlang and Elixir, the natural abstraction to maintain a persistent connection is a process. In this post, we���ll have a look at how we can take advantage of the gen_statem behaviour to write state machine processes that act as persistent connections to external systems.