RPO(Recovery Point Objective) is a common term in business continuity. In the context of a database system, it describes the amount of data that may be lost following an unexpected outage before it is once again operational. It's important to understand this at an early stage because it will drive decisions such as node count, data synchronization methods, and backup technologies
RTO (Recovery Time Objective) this is the amount of time an outage of the database layer may last. Often, it is incorporated into a Service Level Agreement (SLA) contract presented to clients or assumed as a metric within the application stack. Like RPO, this is a contractual-level element that can determine the number of required nodes at steadily increasing expense as the amount of tolerable downtime decreases.