Derby is a full-stack framework used to author real-time, collaborative applications. Built with Express.js, Derby uses an MVC (Model-View-Controller) architecture that comes with Racer, a powerful data synchronization engine that automatically syncs data among servers, databases, and browsers and natively supports conflict resolution. In addition to Racer, Derby offers myriad tools to handle such tasks as data binding, routing, and template rendering, among others. All of these features run the same code, regardless of whether they are running on the server or in a browser, so that no code duplication is necessary. Derby adheres to Node.js conventions and can use popular socket libraries and databases, including MongoDB, Google’s BrowserChannel, Stylus, LESS, UglifyJS, and Express.js.