From 25 Minutes to 7 Minutes: Improving the Performance of a Rails CI Pipeline

We recently hit a new record at Gusto: 6 minutes and 29 seconds.That time is how long it took to run the test suite for our largest application at Gusto, a Rails monolith. This is the fastest our continuous integration (CI) had ever run in the company’s recent history. This last time our CI suite ran this fast, the whole company could fit in a conference room. Now we’re several hundred engineers located around the world working out of a Rails monolith that powers.