This was an interesting talk. I watched this video after working on DF for quite some time, my mental model for logical plan & expr tree improved. Thank you @andrewlamb11
The slides are docs.google.com/presentation/d/1ypylM3-w60kVDW7Q6S99AHzvlBgciTdjsAfqNP85K30. For some reason RU-vid won't let me post them directly in the links. andrew.nerdnetworks.org/ has more