The Limits of the CAP Theorem
It&#x27;s kind of amazing how we have to have this discussion again every time somebody designs a CP system with excellent availability.<p>I&#x27;ll just come out and say it: the &#x27;A&#x27; in CAP is boring. It does not mean what you think it means. Lynch et al. probably chose the definition because it&#x27;s one for which the &#x27;theorem&#x27; is both true and easy to prove. This is not the impossibility result with which designers of distributed systems should be most concerned.<p>My heuristic these days is that worrying about the CAP theorem is a weak negative signal. (EDIT: This is not a statement about CockroachDB&#x27;s post, which doubtless is designed to reassure customers who are misinformed on the topic. I&#x27;m familiar with that situation, and it makes me feel a deep sympathy for them.)<p>(Disclosure: I work on a CockroachDB competitor. Also none of this is Google&#x27;s official position, etc., etc. For that, here&#x27;s the whitepaper by Eric Brewer that we released along with the Cloud Spanner beta launch <a href="https:&#x2F;&#x2F;static.googleusercontent.com&#x2F;media&#x2F;research.google.com&#x2F;en&#x2F;&#x2F;pubs&#x2F;archive&#x2F;45855.pdf" rel="nofollow">https:&#x2F;&#x2F;static.googleusercontent.com&#x2F;media&#x2F;research.google.c...</a>).