Architecting Offline-First Progressive Web Apps with IndexedDB & Service Workers

### 1. The Reality of Low-Bandwidth Connectivity In many Tier-2 and Tier-3 educational environments, continuous high-speed broadband cannot be assumed. An accessible education platform must function seamlessly during intermittent dropouts and low signal. ### 2. Client-Side Storage Architecture - **Service Worker Precaching**: Serving HTML, CSS, and brand assets directly from CacheStorage on subsequent visits. - **IndexedDB for Curriculum Modules**: Allowing learners to explicitly tap "Download for Offline" to store lesson text, code snippets, and knowledge checks locally on their device. - **Asynchronous Sync Queue**: Storing lesson completion events and quiz attempts in an offline queue, syncing to PostgreSQL when connectivity returns. ### 3. Conflict Resolution Using optimistic UI updates with deterministic timestamp resolution ensures learners never lose progress made while travelling or working disconnected.