Today I've finally tested proxysql on a galera setup. Just the read/write-split feature resulted in quite some perfomance gain. After a load test I selected the 5 top queries for caching (ttl 60 seconds), fired up the same load test, and the requests were twice(!) as fast. Without any real fine tuning. I'm impressed.
ProxySQL
ProxySQL: high-performance, GPL licensed MySQL proxy. It supports hundreds of thousands of concurrent connections and can be multiplexed to hundreds of servers.
