The story begins on August 12th, 2015, not even one year after the Elixir 1.0 release. Phoenix is on version 0.16.1, Ecto callbacks haven’t been deprecated yet. My current boss pushes our first Elixir commit to Gitlab.

ElixirConf is happening on September 4th, 2018. Three years and 60 thousand lines of code later, the project is still alive, serving one million registered users. We’re now on Elixir 1.6 and Phoenix 1.3. Ecto callbacks are long gone and only few of us can remember them.

A lot has changed. We’ve made a lot of mistakes. This is a success story, though. Running the same project for such a long time gave us a unique opportunity to observe how the language changed and became really mature. This talk will try to share some of the lessons learned during this time and insights on how changes in the ecosystem affected our codebase.