In Firebase, we all know that data is stored in JSON tree format, which is synchronized in realtime to every connected device. So while building cross-platform applications (web, iOS, and Android) with Firebase, we can share one instance to all your apps to receive the latest updates with new data from Realtime Database. So when we add the data into the JSON tree, it becomes the node in the existing JSON Structure with an associated key, so we always need to plan how data will be saved to build a properly structured database.