At Stripe, we manage a codebase of tens of millions of lines of Ruby. Like any large codebase, people have no shortage of complaints about it, and it's our job to fix those complaints. Fixing them means refactoring the problems away, and over the years we've learned what it takes for these sweeping refactors to be successful: it comes down to leverage and ratcheting.

We'll use two examples to talk about what it means to have leverage over a codebase and how to ratchet increment progress: how we built a Ruby type checker to make developers happier, and how we're building a Ruby package system to introduce modularity. The ideas will be high-level, and apply to basically any team that wants to run a migration in a large, stubborn codebase.

Click here to view the live version of the slides.