The mechanics of local storage for session recovery

When a browser tab crashes or a system update forces a restart, your progress in a study session should not vanish. We use local storage to cache state updates locally before they sync with the primary database. This approach prioritizes data persistence over immediate server synchronization. You can resume your work without manual intervention.

The write-ahead strategy

Every time you answer a question or update a flashcard state, the application writes a snapshot to the browser local storage. This occurs on the client side. We do not wait for the server to acknowledge receipt of the data before allowing you to proceed to the next card. This keeps the interface responsive during periods of high latency. If the connection drops, the browser continues to hold the most recent state of your session locally. The server is notified of these changes only once the network connection stabilizes or when the session concludes.

Resolving conflict states

Storing data locally introduces the risk of state drift. If a user logs into the same account on a different device, the local storage on the primary machine might conflict with the server state. We resolve this by appending a timestamp to every state update. When the application initializes, it compares the timestamp of the local cache against the last successful server save. The application selects the most recent update as the authoritative source. If the local cache is stale, the application discards it and fetches the current progress from the server database. This method avoids data duplication and ensures your history remains linear.

Limitations of browser storage

Local storage is limited to approximately 5MB per domain. This is sufficient for session metadata and recent study history, but it cannot house your entire library of uploaded documents. We maintain a strict boundary between what resides locally and what resides on the server. Your primary study materials are always fetched from our cloud infrastructure. The local storage layer serves only as a temporary buffer for session activity. If you clear your browser cache or use private browsing mode, this persistent layer is destroyed. In those specific scenarios, the session state defaults to the last successful server checkpoint. We recommend using a stable connection for intensive sessions to ensure the synchronization queue clears frequently.