Our 13 years old Ruby on Rails app is well maintained and ~stable~boring. Dealing with many unstable vendors, networks, and co-workers we’ve struggled to keep track of our processes within the application and maintain an audit trail. We’ve been applying patches to symptoms ever since. When we finally decided to pivot in 2020 and switched a core part of the application to Event Sourcing we immediately felt the relief of a reliable, traceable process but also learned our lessons in introducing such a pattern to an existing app. And now, it’s time to share these…