High availability setups are absolutely required to upgrade / patch running databases as well without significant downtime. The engineering and business costs in time to try to work around these issues are from the 90s and have no place in a modern business environment. Heck, they figured out HA decades before then in commercial, proprietary DBs. Things are much more reliable now with OSS tools than even 4 years ago to the extent few talk about it anymore. There are definitely mistakes and bugs possible but the number of _successful_ failover and failback events must be considered in the calculus.

Upgrades aren’t to be taken lightly of course but again, it’s now a cost of doing business and a reality that we need to engineer properly for.