CAP理论   Eric Brewer , systems professor at the University of California, Berkeley, and at that time head of Inktomi, brought the different trade-offs together in a keynote address to the PODC (Principles of Distributed Computing) conference in 2000.1 He presented the CAP theorem, which states that of three properties of shared-data systems—data consistency, system availability, and tolerance to network partition —only two can be achieved at any given time.   Eventually Consistency one of the weak consistency. That is, if no more updates on the given object, accessing the object will always return the last updated value. Of couse, there is a time period between the update and all observers seeing the updated value, which called inconsistency Window.