Flutter offline sync: what holds on Carnet de Bord

Carnet de Bord must work in a parking lot with no 4G. If a trip vanishes, the driver (and RSE payroll) pays. Here is what I kept after several iterations.

Non-negotiable order

1. Write locally (immediate source of truth)
2. Mark “pending sync”
3. Push to Firestore when connectivity allows
4. Show an honest UI state (no eternal spinner)

// Flow spirit — not the exact file
await localStore.saveTrip(trip);
syncQueue.enqueue(trip.id);
unawaited(syncService.flush());

Conflicts

I did not build a CRDT. Last-write-wins + server timestamps are enough for this trade. Two devices editing the same day is rare; a perfect merge is not worth the product delay.

Next

The Laravel site also hosts Flutter Web under /app/ — same product, other surface. Offline discipline stays native-mobile-first.