The foundational technology for Muse 2 is local-first sync, which draws from over a decade of computer science research on CRDTs. Mark, Adam Wiggins, and Adam Wulf get technical to describe the Muse sync technology architecture in detail. Topics include the difference between transactional, blob, and ephemeral data; the “atoms” concept inspired by Datomic; Protocol Buffers; and the user’s data as a bag of edits. Plus: why sync is a powerful substrate for end-user programming.