> Changing from master to replica is easy, but now you have to rebuild that original master off of the former replica now. Completely start over. You can't just start up again from a given transaction ID. MySQL's GTID implementation is much better in this regard. You can change masters and replicas all repoint them without rebuilding. You can't do that (currently) with Postgresql.
Have you heard of pg_rewind? https://www.postgresql.org/docs/current/static/app-pgrewind....