RTO (Recovery Time Objective) is a metric that determines the maximum amount of time that a service can be unavailable or disrupted before it causes unacceptable consequences for the business. RTO is normally measured in minutes, hours, or days, and it is based on the criticality and priority of the service. RTO is one of the key metrics that can determine the service recovery duration, as it defines the target time frame for restoring the service to normal operations after a disaster. For example, if a company has an RTO of four hours for its email service, it means that it aims to recover the email service within four hours after a disaster, such as a server failure or a network outage.