I usually say that application development (mobile and otherwise) is a solved problem but once you go to any kind of scale, you run into all of these operational issues which keep things interesting.

“75 jaar vrijheid, en wat krijg je? De lichtgevende lul van Daan Roosegaarde.”

Figma’s multiplayer support is fantastic and something similar should be a part of every creative application. Now they’ve also written a very understandable high-level overview of their implementation (with CRDTs).