Quick answer: Unreal Iris state history (used for rollback) reset on server restart? History lives in memory; restart clears - persist history snapshots for cross-restart rollback.
Server crashes mid-match; restart loses the rewind ability for the live match.
Persist snapshots
Periodically write Iris history to disk. Restart loads; rollback up to last persisted point.
Or reset to known state on restart
Restart loads the canonical session state. Rollback isn't possible; predictability is.
Skip rollback after restart
Disable rollback for 5 seconds after restart. Clients re-sync; system stabilizes.
“Rollback is a memory feature. Memory is volatile; restarts erase.”
If you offer rollback in a long-running multiplayer game, plan the restart story. Without a plan, restarts mean degraded UX.