Comment by CharlesW

> I thought rails had fallen out of favor at least 5 years ago (deservedly in my biased estimation).

For the folks downvoting, GitHub said basically this in 2018: https://www.theregister.com/2018/08/16/github_rails_microsof...

"GitHub is about a third of the way through an architectural change that began last year. The company is moving away from Ruby on Rails toward a more heterogeneous, composable infrastructure."

This doesn't mean that they're rewriting Rails infrastructure for the sake of it, so legacy Ruby/Rails software will presumably power big chunks of GitHub for many years to come.