I don't understand why someone would choose to deploy anything mission critical without having an support contract with the ISP, the manufacturer of the the software etc.
Simple, the cost of an outage is less than the cost of a support contract. Very few things are really mission critical as in they can never go down. Rather they simply have a cost to going down and you can choose to pay that one way or another.
I transitioned from collocation to self managed remote server farm and then onto self managed remote vms. All these providers provided de-facto support whether we opted for one or not. You can go to their portal and raise a ticket.
I am not saying with vast numbers its feasible but big cloud providers don't even give you the opportunity to raise a ticket if its their fault. There is a price you pay extra when you opt for any one of them but many don't realize. Having said that - almost all the time, our skilled expertise is better than their initial two level of support staff. We realized it early so we handle it better by going over the documentation and making our code resilient since all cloud platforms have some limit or another since overselling in a region is something they can't avoid. Going multiple regions across when you handle these exceptions is the only way through.
