We don't use Patroni or any of the other off the shelf items. We rolled our own primarily from our years of experience on Heroku Postgres. We're actually working on a detailed post on how HA and disaster recovery works for Citus Cloud, though the core mechanism powering it all under the covers is our state machine. You can read a bit about how it works in this post: https://www.citusdata.com/blog/2016/08/12/state-machines-to-...