Most discussions about Docker are from the deployment point of view – how to get your app to run in a container, and spread those containers out, turn them on and off to make your application more scalable. But Docker is a very useful tool for developers, too, and that purpose gets lost in the DevOps discussions. Want to play with Mongo? Want to test your app with a new version of the database? Or maybe you just want to use something else instead of the always-in-flux dev database server? You can do that locally, and easily, with Docker. And then turn those services on and off with one command. You don’t have to add all those extra dependencies on your machine either. You may never do brew install some-large-package ever again.