@Override
  public long getLastSequenceId(String encodedRegionName, String peerId)
    throws ReplicationException {
    byte[] qual = Bytes.toBytes(encodedRegionName);
    try (Table table = conn.getTable(tableName)) {
      Result result =
        table.get(new Get(Bytes.toBytes(peerId)).addColumn(LAST_SEQUENCE_ID_FAMILY, qual));
      byte[] lastSeqId = result.getValue(LAST_SEQUENCE_ID_FAMILY, qual);
      return lastSeqId != null ? Bytes.toLong(lastSeqId) : HConstants.NO_SEQNUM;
    } catch (IOException e) {
      throw new ReplicationException("failed to getLastSequenceId, encodedRegionName="
        + encodedRegionName + ", peerId=" + peerId, e);
    }
  }
HBase table based replication queue storage.
hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/TableReplicationQueueStorage.java