The story
PriceWatch Pro came to us with a working prototype that broke whenever a retailer shipped a markup change. We rewrote the content-script layer with selector profiles per retailer, moved long-running work into a service worker with chrome.alarms, and added a tiny IndexedDB-backed price history that syncs across the user's machines via chrome.storage.sync.
The popup is a 12 KB React bundle with an option to drill into a 30-day chart per product. The service-worker logic has zero direct DOM dependencies, so retailer changes are now patched in one selector file instead of touching application code.
