This document provides an overview of Couchbase Server and how to use it with Ruby. Couchbase Server is a NoSQL database that supports automatic key sharding and replication. It is used by companies like Heroku and Zynga. The document outlines how to install the Couchbase Ruby gem, perform basic CRUD operations, use optimistic locking, expiration, map/reduce, and integrate Couchbase with Rails and other Ruby frameworks.