any well built service architecture doesn’t require a massive head count of engineers to keep things running. if code isn’t constantly changing because of new features, it’s behavior should be same. If traffic increases, more hardware will automatically get provisioned and added behind your load balancers, and lbs should auto scale as well.

you must need a few support staff which you can hire contractors for to keep things like OS and other software dependencies patched with latest updates.. and if u using third party cloud, depending on abstraction you get this taken care of as part of the package.