your question is very interesting: based on my experience, i think there isn't a unique answer as several types of KPIs have to be analyzed based on the company process you have to evaluate. As an example, based on supply chain side, KPIs could be defined on e.g. days to recover the replenishment process; if you consider internal operation in a firm, KPIs could be days or hours to restart the production. This a topic not completely analyzed in the litterature!