How an Offline-First PWA Keeps Blood Donor Searches Running Inside Hospitals

Badhan, a blood donation volunteer network linked to Dhaka Medical College Hospital and run by students of Amar Ekushey Hall at the University of Dhaka, faced a critical challenge: hospital buildings with thick concrete walls and basement floors routinely block mobile connectivity. To solve this, developer Parvej Shah built an offline-first Progressive Web App that stores all donor records, blood group data, and contact information locally in the browser's IndexedDB, so searches run without any network connection. Unlike merely offline-capable apps that degrade gracefully, this system treats local storage as the primary data source and uses network access only to sync updates from the server. The app also pre-computes each donor's eligibility based on a mandatory 90-day gap between donations at sync time, ensuring instant filtering during time-sensitive searches. Service worker caching via Workbox further ensures the app loads and functions fully even when volunteers are deep inside hospital infrastructure with no signal.