We talk with Marc-André Lafortune about reducing Elixir project compile times. On larger projects, when a single file like a view template is changed and over 100 files get recompiled, there is something wrong. Marc-André explains how he identified the problems in his project and contributed to Elixir’s mix xref tool making it easier for us to find those problems in our own projects! We cover how these tooling improvements were used to improve the upcoming Phoenix 1.6 and Elixir 1.13! An additional mix xref flag was added to run CI checks on our code to prevent accidentally adding code that slows our compile times.