When implementing offline functionality for mobile app performance, there are various techniques to consider, depending on the features and logic that need to be supported when the network is unavailable. For example, a service worker can be used to intercept and handle network requests, such as fetching cached data or performing background tasks. This is especially useful for progressive web apps (PWAs) that run on a web browser. Additionally, libraries or frameworks like Workbox or Ionic can help simplify the service worker creation and registration process. Additionally, local storage can be used to store data that can be accessed and modified offline, such as drafts, notes, or bookmarks. SQLite or Realm can be used for native apps while IndexedDB or Web Storage can be used for PWAs. It is also important to use a conflict resolution strategy, such as last-write-wins or merge, to resolve any discrepancies between the local storage and the remote database when the network is restored. Lastly, a network detection and notification system should be used to monitor and inform the user about the network status. The Network Information API or the Online and Offline Events for PWAs, or the ConnectivityManager or Reachability for native apps can detect any changes in the network. A UI component like a banner, toast, or snackbar should also be used to notify users about any changes in the network status and any actions they can take.