Page History

...

The leaderState is extended to reference the KRaftControlRecordStateMachine, from which derives the voter set history. Using this information the of high watermark within LeaderState, the committed voter set can be obtained directly from KRaftControlRecordStateMachine. Both the voter set in the KRaftControlRecordStateMachine and the high watermark are maintained entirely in memory. This eliminates disk I/O, there by, minimizing performance impact.

Scenario

Committed voter present in voters/observers
If a committed voter is also present in the current voters or observers set, its ReplicaState is identical to the corresponding entry in those sets. This ensures that all runtime fields within ReplicaState are available.Committed voter absent from voters or observers 

Committed voter absent from voters or observers
If a committed voter is not found in either voters or observers, certain runtime-specific fields cannot be derived, since the replica is no longer actively participating in log replication. To maintain schema consistency, these fields in its ReplicaState are set to sentinel values:

• hasAcknowledgedLeader = false

• endLogOffset = -1

• lastFetchTimestamp = -1

• lastCaughtUpTimestamp = -1

These Above fields are only meaningful for active replicas(voter) in the quorum. For committed voters, they are not strictly required—the sentinel values simply indicate that the data is unavailable or not applicable.

...