well this is probably PR as there is no such system nor it can be made that can have 100% uptime. not talking about the fact that network engineers rarely work with servers :)
Not 100% but 99.9%… IIRC Guild Wars 2 servers had like 1 actual outage in 11 years. They have pretty amazing structure.
Fun fact, uptime goals are measured in nines – for example, 99.9% is three nines of uptime. If that one outage lasted an entire day, and they were never down at any other time, that would indeed be three nines of uptime.
Yeah, my net admin colleagues explained that one to me a while back because the bosses were making similar uninformed demands (“this needs to never go down!” “Sure, here is how much that costs”). It was very enlightening :)
a lot of things are possible if you are lucky enough ;)