Brent Sordyl's blog

In the mid-’90s, with the rise of larger Internet systems, these practices were revisited. At that time people began to consider the idea that availability was perhaps the most important property of these systems, but they were struggling with what it should be traded off against. 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. A more formal confirmation can be found in a 2002 paper by Seth Gilbert and Nancy Lynch.4
(Link: Eventually Consistent – Revisited – All Things Distributed)