The Couchbase team did a great job putting together this fairly-reasoned analysis. It gives side-by-side comparisons of Postgres’ JSON query syntax and SQL++/N1QL, which is the query language used in Couchbase. It touches on indexes, performance, ergonomics, and finally where each is a good fit.

I’ve personally found that Postgres’ JSON data types provide just enough document-orientation that I can sprinkle in where it makes sense in our data models. But, as with all things in developer-land, YMMV!

NuSTER can be used as a RESTful NoSQL cache server, using HTTP POST/GET/DELETE to set/get/delete Key/Value object. It can be used as an internal NoSQL cache sits between your application and database like Memcached or Redis as well as a user facing NoSQL cache that sits between end user and your application. It supports headers, cookies, so you can store per-user data to same endpoint.