api/java/src/main/java/com/navercorp/redis/cluster/BinaryRedisCluster.java
public Long append(final byte[] key, final byte[] value) {
        client.append(key, value);
        return client.getIntegerReply();
    }
public Long append(final byte[] key, final byte[] value) {
        client.append(key, value);
        return client.getIntegerReply();
    }
Strings