Map/Reduce Views and Indexes
Distributed Architecture with Replication
CouchDB was designed with bi-direction replication (or synchronization) and off-line operation in mind. That means multiple replicas can have their own copies of the same data, modify it, and then sync those changes at a later time.
Built for Offline
Benefits of CouchDB
JSON Documents – Everything stored in CouchDB is a JSON document.
RESTful Interface – From creation to replication to data insertion, every management and data task in CouchDB can be done via HTTP.
N-Master Replication – Unlimited amount of ‘masters’, making for some very interesting replication topologies.
Built for Offline – CouchDB can replicate to devices (like Android /IOS phones) that can go offline and handle data sync for you when the device is back online.
Replication Filters – Filter precisely the data you wish to replicate to different nodes.