Edited on Sep 12, 2016 to correct the description of how ProxySQL handles session variables. Many thanks to Francisco Miguel for pointing this out. ProxySQL is becoming more and more popular as SQL-aware load balancer...

Galera cluster has known limitations, one of them is that it uses cluster-wide optimistic locking. This may cause some transactions to rollback. With an increasing number of writeable masters, the transaction rollback rate may increase, especially...