Background: Imagine a mobile phone or a navigation system in your car. Such systems are sometimes in power-off state (aka turned-off). When users power-on (turn on, power-up, start) the system, they want them to be operational (aka usable) in a relatively short time.
This also holds for systems that are automatically managed, e.g. services deployed in the cloud.
Metric: The system must be able to start from power-off to operational state in less than 90 seconds.