Offline & Resilience

Resilience is built around a local datastore (WatermelonDB on mobile, IndexedDB on web) that holds the working set the device actually needs — current competition draws, score entry, cached license bundles for verification, and the participant roster for QR check-in. Every write goes to the local store first and is journalled into a per-table change log keyed on a delta timestamp; the user sees a sync-status indicator showing pending, completed, failed and conflict counts in real time.

When the radio comes back, a WatermelonDB-compatible pull/push protocol exchanges deltas with the API. Pushes are idempotent and version-tagged so a flaky uplink can retry safely; pulls stream only what changed since the last successful checkpoint. Conflicts are resolved by per-resource-type policies (last-write-wins, server-wins, client-wins or manual queue) with field-level auto/manual classification, and every resolution is recorded in a ConflictAuditEntry so a club admin can inspect after the fact why a score line moved.

License bundles are signed with HMAC-SHA256 so an offline scan can verify legitimacy even days into a no-signal weekend; incremental delta downloads use a previous_hash chain to keep payloads small. The platform enforces a configurable maximum offline window (default seven days, twelve-hour grace, five-day warning), invalidating expired offline data so a long-disconnected device cannot stamp records with stale identities. Selective sync lets a referee scope storage to one specific competition, and a connection-aware profile (wifi / 5G / 4G / 3G / 2G / ethernet) tunes batch size, image inclusion, compression and throttling. Background sync respects per-user wifi-only preferences and quiet hours; for the worst case there is a documented manual fallback — paper score sheets that can be photographed and OCR-ingested later.