Mnesia predates the CAP theorem so perhaps that is why the author feels it doesn't specifically fit into AP or CP. You can't design your system around something

Mnesia predates the CAP theorem so perhaps that is why the author feels it doesn't specifically fit into AP or CP. You can't design your system around something that doesn't exist yet! Though, the qualities that CAP tries to represent were probably still on their mind albeit in a less formalized way.