Apache CouchDB is a document-oriented database that can be queried and indexed in a MapReduce fashion using JavaScript. CouchDB also offers incremental replication with bi-directional conflict detection and resolution. CouchDB provides a RESTful JSON API than can be accessed from any environment that allows HTTP requests.

CouchDB is written in Erlang, a robust functional programming language ideal for building concurrent distributed systems. Erlang allows for a flexible design that is easily scalable and readily extensible.