Setup proxysql read-write split with both galera cluster and master slave replication

I have the following setup: 1. Three node galera cluster (galera-1, galera-2, galera-3) 2. galera-2 is master to slave-1 (master-slave replication) 3. slave-1 is master to both slave-2 and slave-3 4. slave-1, slave-2 and slave-3 have read_only = 1 I have the following ProxySQL configuration: mysql_servers = ( { address = "galera-1" port = 3306 hostgroup = 2 }, { address = "galera-2" port = 3306 hostgroup = 2 }, { address = "galera-3" port = 3306 hostgroup = 2 }, { address = "galera-2" port = 3306 hostgroup = 5 max_replication_lag = 5 }, { address = "slave-1" port = 3306 hostgroup = 5 max_replication_lag = 5 }, { address = "slave-2" port = 3306 hostgroup = 5 max_replication_lag = 5 }, { address = "slave-3" port = 3306 hostgroup = 5 max_replication_lag = 5 } ) mysql_galera_hostgroups = ( { active = 1 backup_writer_hostgroup = 4 max_transactions_behind = 100 max_writers = 1 offline_hostgroup = 1 reader_hostgroup = 3 writer_hostgroup = 2 writer_is_also_reader = 0 } ) mysql_replication_hostgroups = ( { writer_hostgroup = 5 reader_hostgroup = 6 } ) With this configuration: - Available servers for **writing**: - hostgroup 2 (I will always be routing to this one) - hostgroup 5 - Available servers for **reading**: - hostgroup 3 - hostgroup 4 - hostgroup 6 How can I route **read** queries to hostgoups 3, 4 or 6 in a round-robin fashion? mysql_query_rules = ( { rule_id = 100 active = 1 match_pattern = "^SELECT .* FOR UPDATE" destination_hostgroup = 2 apply = 1 }, { rule_id = 200 active = 1 match_pattern = "^SELECT .*" destination_hostgroup = 6 apply = 1 }, { rule_id = 300 active = 1 match_pattern = ".*" destination_hostgroup = 2 apply = 1 } ) I've tried mixing groups between Galera and MySQL replication but things get mixed up quite badly. Is there a way to create a hostgroup of hostgroups so I can route to the "group of groups"?