The application uses Couchbase Server as the central repository of data, while using Couchbase Sync Gateway to synchronize data between mobile devices in real-time. The Node.js application uses a RESTful API to interact with both Couchbase Server and Couchbase Sync Gateway. The application has two endpoints: one for listing data from Couchbase Server and another for creating data that is then synced to Couchbase Server through Couchbase Sync Gateway. The application demonstrates how to use the Couchbase SDKs in Node.js to interact with a Couchbase Server cluster, as well as using Couchbase Sync Gateway to synchronize data between mobile devices.