"by Karen Casella, Phillipa Avery, Robert Reta, Joseph Breuer\n\nEarly in 2016, several Netflix teams were asked the question: “What would it take to allow members to download and view content offline on their mobile devices?”\n\nFor the Playback Licensing team, this meant that we needed to provide a content licensing system that would allow a member’s device to store and decrypt the downloaded content for offline viewing. To do this securely would require a new service to handle a complex set of yet-to-be defined business validations, along with a new API for client and server interactions. Further, we determined that this new service needed to be stateful, when all of our existing systems were stateless.\n\n“Great! How long will that take you?”\n\nIn late November 2016, nine short months after