Low / zero downtime is totally achievable with pg_logical and really boils down to whether or not you want to try to adopt bi-directional writes (and conflict management / integrity issues), or if you're willing to just have a brief session termination event and swapover. To me, the latter has generally been preferable as conflict management systems tend to be more complicated in reality (based on business logic / state) than what pg_logcical provides. Interested if people here have had success with bi-directional writes though.