Another approach is you start up a full copy of the new system with all new versions, then change loadbalancers to direct all traffic away from the old system and to the new. Then decomission the old system.
With dedicated hardware, you need twice as much hardware. With cloud, you only pay double for 10 minutes during the rollout, which usually is very cheap.
With dedicated hardware, you need twice as much hardware. With cloud, you only pay double for 10 minutes during the rollout, which usually is very cheap.