public void finishIteration() {
    this.replicaStatus = ReplicaStatus.UNKNOWN;
    this.throttledTill = time.milliseconds() + throttleDurationMs;
  }
whenever a group is finished, this method gets called for corresponding replica trackers,
replica status is moved to unknown and replica is throttled
ambry-replication/src/main/java/com/github/ambry/replication/continuous/ReplicaTracker.java