@Override
    public void onPartitionBecomeStandbyFromLeader(String partitionName) {
      logger.info("Partition state change notification from Leader to Standby received for partition {}",
          partitionName);
      if (leaderBasedReplicationAdmin != null) {
        // Remove the leader partition from the in-mem structure maintained in leaderBasedReplicationAdmin.
        // LeaderBasedReplicationAdmin::removeLeaderPartition is thread safe.
        leaderBasedReplicationAdmin.removeLeaderPartition(partitionName);
      }
    }
{@link PartitionStateChangeListener} to capture changes in partition state.
ambry-replication/src/main/java/com/github/ambry/replication/ReplicationManager.java