This talk distills the lessons we’ve learned at Felt while building a highly collaborative, “multiplayer” editing tool on top of Phoenix and React. Phoenix Channels are our (not so) secret weapon for delivering low-latency collaboration, but Channels alone aren’t enough to guarantee a delightful experience for our users. This talk will discuss a number of areas where our initial ideas didn’t cut it and what we had to do instead to improve the user experience. Topics will include: - Minimizing time to first render - Using optimistic client-side changes for zero-latency local editing - Reducing latency when broadcasting changes - Preventing data loss when the client goes offline - Reducing blocking work within the Channel process