[pbailis]

Unlike "C" and "A" in "CAP," "AC&D" (specifically, "C") can't be easily separated from "I".

Serializability ("I") ensures that database consistency, or maintenance of integrity constraints ("C"), is not violated. While it's possible to get consistency ("C") without serializability (which would give up traditional "I" in favor of a weaker form of isolation), it's often difficult [see http://www.bailis.org/blog/when-is-acid-acid-rarely/#arbitra...].

[lucian1900]

Things like MongoDB fail at A and D, which is what the parent was probably thinking of.

[willlll]

It also fails at C for concurrent writes

[lucian1900]

Sure, but A and D are the particularly embarrassing ones.