The CAP FAQ
Henry Robinson (via Hacker News):
No subject appears to be more controversial to distributed systems engineers than the oft-quoted, oft-misunderstood CAP theorem. The purpose of this FAQ is to explain what is known about CAP, so as to help those new to the theorem get up to speed quickly, and to settle some common misconceptions or points of disagreement.
(Hat tip to my mentor Nancy Lynch, who proved the theorem.)