If you look at how Phoenix handles in its code, you will get an Idea. Specifically, org.apache.phoenix.query.QueryConstants.java defines zero byte separator as below public static final byte SEPARATOR_BYTE = (byte) 0; public static final byte[] SEPARATOR_BYTE_ARRAY = new byte[] {SEPARATOR_BYTE}; You can use Bytes.add(byte[], byte[]) to append separator byte array to form a composite row key. Let me know,How it works... ... View more