How does Scala support high-scale event replay systems?

Event replay reconstructs system state by reprocessing stored event logs.

Event replay is central to event sourcing architectures in Scala. Systems like Akka Persistence or Kafka log streams store immutable events. State is rebuilt by replaying events from the beginning or a snapshot. This enables auditing, debugging, and system recovery. Replay systems must ensure determinism, meaning identical inputs always produce identical state.