This is the story of a Rails app that was from day 1 architected with a large scalable codebase worked on by a big dev team in mind. Learn about the problems we solved and lessons we learned: how to partition your Rails app into distinct modular engines, how to speed up your test suite by only running code effected by your changes, how to add a layer on top of ActiveRecord to enforce loose coupling, and many more!
Rails code bases get gnarly when you don't take the time to think about architecture. I think this talk with ring true and turn on a light for a lot of people. It talks about problems that people can relate to, as well as gives solutions for them.