Consistency: Database is consistency. A read after a update should receive new data.
Availability: High availability mean every requests should be succeed and receive a respond.
Partition-Tolerant: the service should be able function when part of network fails.
Eric Brewer, a University of California, Berkeley professor and the co-founder and Chief Scientist of Inktomi, in a 2000 Principles of Distributed Computing (PODC) talk, stated it was impossible for distributed web services to guarantee consistency, availability and partition-tolerance.
Amazon S3 guarantees availability and partition-tolerance but does not guarantee consistency. Mnesia sacrifice P for CA.
