Yeah... that's a Rails callback, not an SQL constraint, and can't be relied upon in the face of multiple simultaneous requests. Which kind of demonstrates my point. With a custom API, you have to understand your system, it's requirements, and it's limitations. You can't just read a blog post on "securing your webapp" and assume it's good.

Couch is no different. You have to understand Couch, you have to understand it's features and limitations, and build your system within those constraints.

You seem to be asserting because Couch is designed to be internet connected it can't be secure. If that's true, then I guess every customer on IBM Cloudant (Couch as a service), Realm (another database designed for mobile sync), and Firebase (Google database as a service) are all in trouble and just don't know it yet.

Security for all systems is non trivial. Thinking it is assures your system is not secure.