long getTimestamp(int keyLength) {
    int offset = getTimestampOffset(keyLength);
    return ByteBufferUtils.toLong(this.buf, offset);
  }
This Cell is an implementation of {@link ByteBufferExtendedCell} where the data resides in off
heap/ on heap ByteBuffer
hbase-common/src/main/java/org/apache/hadoop/hbase/ByteBufferKeyValue.java