[bouncing]

If the military has fighters that can refuel in the air, why does United refuel on the ground like chumps?

First of all, sometimes even AWS makes mistakes and has downtime. They have downtime (usually unplanned) fairly often. Companies like VISA, that do payment processing, where countless dollars could be lost in just a few minutes of downtime, almost never update their old systems. They still have programs running FORTRAN. When they do update, it's complicated.

You can try to get really good uptime by doing things like forking your database and replicating your commit log to the fork. You can do rolling updates, where different customers are served different versions of a system. You can do extremely thorough testing.

But are you? Can you afford to do that and do you even have the engineering talent to make it happen even if you want to? Are you going to pass on new business opportunities and new features just to avoid a 20 minute downtime for a database migration at 2am? I suspect you are not.