“Don’t reinvent the wheel” has always been one of the golden tenants of software engineering — but what happens when the wheel becomes really cheap to reinvent? In the past, buying off-the-shelf software almost always made more sense than building something from scratch, but over the last 12 months, the economics have shifted dramatically, and now all it takes is an engineer getting a little too frustrated with janky SaaS software to build a custom replacement in an afternoon. In this talk, we walk through how we’ve been navigating the build-vs.-buy debate at Cloudflare and how it’s changed a lot of our procurement decisions. We use our custom AI code reviewer as a case study of how we built something from the ground up instead of buying something off the shelf, and we discuss the challenges and hurdles we ran into along the way.