[tharkun__]

Having 4 people is actually not enough I would argue.

BUT!

That's because I advocate for people being able to go on vacations without worrying about work and to be able to not be on-call 24/7/365.

I.e. you don't need them full time and you also need them for all other options, because you need to cover on-call for anything you use. Nobody at AWS or Google will so much as blink when your precious infrastructure blows up on you and you don't know what to do. You need brains to work on those things yourself. You want to only have people on-call every 5 or 6 weeks.

How exactly to calculate the percentages on those salaries, that I am not sure of, but it definitely isn't a full time job to babysit infrastructure like that with 4 full-time brains doing nothing but watching your monitoring dashboards!