Chapter 5
CouchDB

Ratchet wrenches are light and convenient tools you carry around for a range of jobs, big and small. As with power drills, you can swap out variously sized bits like sockets or screws. Unlike a power drill that needs to be plugged into 120 volts of AC power, however, a wrench is happy to rest in your pocket and run on elbow grease. Apache CouchDB is like that. Able to scale down as well as up, it fits problem spaces of varying size and complexity with ease.

CouchDB is the quintessential JSON- and REST-based document-oriented database. First released all the way back in 2005, CouchDB was designed with the web in mind and all the innumerable flaws, faults, failures, and glitches that come with it. Consequently, CouchDB offers a robustness unmatched by most other databases. Whereas other systems tolerate occasional network drops, CouchDB thrives even when connectivity is only rarely available.

Like MongoDB, CouchDB stores documents—JSON objects consisting of key-value pairs where values may be any of several types, including other objects nested to any depth. What you don’t get, though, is ad hoc querying. Instead, indexed views produced by incremental mapreduce operations are the principal way you discover documents.