Is it possible to join MySQL 8.0 to a cluster of MySQL 5.7 I have a MySQL 5.7 (5.7.19-17-57-log Percona XtraDB Cluster) cluster using Galera, but I am in the middle of upgrading to 8.0 -- 8.0.23-14 Percona Server (GPL), Release '14'.  I wasn't sure if it was possible to join the 8.0 box to the clustered 5.7.
It's not possible to make a Percona MySQL server 8.0 join a Percona XtraDB Cluster, regardless of version. The 8.0 server has to be Percona XtraDB, otherwise it won't have the necessary Galera libraries and bindings.