TLOG replica means transaction log replica. Instead of indexing the data again, a TLOG replica reads the transactions logs of the master or leader shard and replicates the segment or indexed data using a replication handler. In case of failure of the leader shard, one of the TLOG replicas acts as a leader and performs real-time indexing. It also makes a copy of the transaction log. Once the leader shard is available again, it again goes to the replica shard mode and performs only binary replication of segments. Replication done using the TLOG replication method is not as real-time as the one done using NRT replicas.