[jahewson]

CAP theorem tells us that you can't have availability without sacrificing consistency or partition tolerance, which means that there isn't a NoSQL database which can do that either.

It is not true that relational databases must have a single point of failure (SPoF) or must use failover: MySQL Cluster is a sharded multi-master distributed database without a SPoF.

On the other hand Redis, for example, is a master-slave failover NoSQL datastore.

[pkolaczk]

CAP theorem says it cannot be done at the same time. But it is perfectly fine to sacrifice consistency for availability at the time partition happens and restore consistency once the partition is fixed. Still better than nothing if revenue counts. Financial institutions do like that all the time.