The rock-solid document-oriented database Apache CouchDB provides an REST API, JSON documents and clustering with a masterless architecture. If the case allows for a document-based database, CouchDB is our choice.
With version two CouchDB implements the Dynamo Paper for even more performance with nearly congruent APIs—a great update to this wonderful open source project.
PouchDB as perfect supplement ports the CouchDB architecture to the client side and thus enables the frictionless replication of data. This symbiosis creates a lot of developer happiness, especially for data-driven apps.
Small tidbit: you can even use PouchDB together with node.js, synching data into your application without the need for a local database.