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-...
"In addition to continuous protection which is explained above, high availability is available if your application requires less exposure to downtime. We provision stand-bys if you select high availability at provisioning time. This can be for your primary node, or for your distributed nodes."
https://docs.citusdata.com/en/v6.1/cloud/features.html
Please let me know if I've missed any resources on this topic!
Yep, our docs are definitely behind the product here, we'll be working to improve. FWIW it would be the closest to the Heroku Postgres HA as it's the same person that wrote both systems.