Honestly, most of them were great. Probably the most captivating one was Ben Tyler's fun exercise in using Riak Core to build a stateful, distributed, fault-tolerant, real-time, impress your cat application.

Chris McCord's keynote was also really interesting, he explained how he implemented Phoenix Presence using a certain kind of CRDT.

And for some laughs I recommend watching Gary Rennie's funny story about achieving 2 million clients simultaneously connected to a single Phoenix server.