Again an engineering problem. You can deploy with zero downtime and people have been doing this for decades. It takes infrastructure like load balancers, ability to run versions in parallel and runtime support for feature flags, but it’s absolutely doable and ultimately just another day in the office for anyone with global operations. A lot of 3rd party tools actually support these workflows for this exact reason.
You gonna pause writes for cutover so while not downtime, specifically for postgres load balancers, ability to run versions in parallel not gonna help you there.
