You'd use the optimistic UI features that LiveView ships with out of the box to handle the arrow click, and you wouldn't await a server round-trip for each keypress, so again that's now how LiveView form input works. For posterity, I linked another blog where I talk exactly about these kinds of things, including optimistic UI and "controlled inputs" for the keyboard scenario: https://dockyard.com/blog/2020/12/21/optimizing-user-experie...

While we can draw parallels to game servers being near users, I don't think it makes sense for us to argue that LiveView should take the same architecture as an FPS :)