[biggerfisch]

Sure, but automating this requires a lot more tooling. In the case described with multiple, widely spread instances, you'll need to be able to

a) Reliably determine which step you are on - this includes both migration steps and application deployments b) Fully automate your deployments from a list of staged code changes ("normal" CD will have issue with this) c) Fully automate migrations _after_ all deployments are complete

Those are all totally possible steps, but they are all going to vary based on your setup, making a drop in solution for this process unlikely to be easy.

Additionally, these are only the steps if everything works! What happens if there's a bug halfway through? You probably want to stop the deployment process and either revert or quickly hotfix. A human-based system can handle this quite easily, but an automated system will need to be able to measure errors and reliably determine if an issue exists.

So its not that this can't be automated, in fact, I know that it has for several large organizations, but the hurdle to get to the full level of automation is rather high and fraught with secondary issues to consider.