Comment by BSTRhino

Yes, I should have a "who is this not for" section somewhere, that's fair enough.

Persistence is actually handled by the server, and then the server inserts an input back into the game state with the result when it's done. So, no issue with I/O.

I see Factorio is doing deterministic lockstep, which like rollback netcode but without the rollback. That makes sense seeing as it is a game with a lot of state and so it would be too expensive to snapshot and rollback all the time. But yes, I think having a game engine which guarantees determinism in all cases could be a useful base for other multiplayer architectures too. Right now Easel only does rollback but maybe it could do more in the future.