If you are running k8s on prem, the "easy" way is to use a mature operator, taking care of all of that.

https://github.com/percona/percona-xtradb-cluster-operator https://github.com/mariadb-operator/mariadb-operator or CNPG for Postgres needs. They all work reasonable well, and cover all the basic (HA, replication, backups, recovery, etc).