If you are using Galera replication, you know that schema changes may be a serious problem. With its current implementation, there is no way even a simple ALTER will be unobtrusive for live production traffic. It is a fact that with the default TOI alter method, Percona XtraDB Cluster (PXC) cluster suspends writes in order [&]

https://www.percona.com/blog/2019/03/25/how-to-perform-compatible-schema-changes-in-percona-xtradb-cluster-advanced-alternative/