Upgrading GitHub from Rails 3.2 to 5.2 | GitHub Engineering

On August 15th GitHub celebrated a major milestone: our main application is now running on the latest version of Rails: 5.2.1! In total the project took a year and a half to upgrade from Rails 3.2 to Rails 5.2. Along the way we took time to clean up technical debt and improve the overall codebase while doing the upgrade. Below we’ll talk about how we upgraded Rails, lessons we learned and whether we’d do it again.