Hosted Chef is one of the biggest Chef installations there is, with tens of thousands of organizations managing hundreds of thousands of Chef clients. By 2015, Hosted Chef had been growing exponentially for several years, and it was quickly outgrowing its home. It was time for a change, and so last October we migrated Hosted Chef from its original data center into AWS. As if the migration of a large production service wasn’t enough, we were using an aging code base with practices and procedures that were years old, with references to CouchDB and workarounds from Chef 0.9! It was time to modernize all of our cookbooks, start using modern features, and generally rewrite everything at the same time. This talk is the story of that migration, the decisions we made, the challenges we faced, and the spectacular results. I’ll cover what worked and what didn’t go so well, and along the way I’ll share some critical insights that will be useful to anyone running a large Chef installation in a cloud environment such as AWS.