A simple way to build collaborative web apps [HN] programming hackernews web apps realtime javascript Sep 1, 2021, 1:54 PMGood article, and some other good recs in the comments
How Figma’s multiplayer technology works design javascript realtime collaboration algorithms multiplayer Jun 22, 2021, 2:59 AMCool write up, some interesting points: operational transforms are complicated (mainly used for text collab) last value written to server wins ignore incoming changes from server while writing, to avoid flicker fractional indexing for reordering for undo, if things were changed (by someone else), that history is updated to prevent conflicts with redo