Mobile offline sync

Warehouses have dead zones; trucks drive through them. The mobile apps are built offline-first so work never blocks on a signal.

What works offline

• View today's trips / tasks (pre-synced on login or last sync).
• Capture events: stop arrive / depart, picks, putaways, counts, PODs, photos, signatures.
• Create exceptions (damage, shortage).
• Read attached documents (trip sheets, BLs, picking lists).

What needs a signal

• Fetching newly assigned tasks since last sync.
• Real-time dispatcher messages.
• Paying / verifying external services (e.g. toll-tag API calls).

How sync works

• App keeps a local SQLite store of all assigned work + captured events.
• Events are queued with a device-assigned id; flushed to server as soon as connectivity returns.
• Server de-duplicates on device-id + timestamp.
• Conflicts resolved server-side: last-writer-wins for most fields; event-log-append for state changes (never silently drop events).

Visibility

• Device shows a sync badge: green (synced < 1 min), amber (< 30 min), red (> 30 min).
• Dispatcher / supervisor dashboards show last-seen-at per driver / operator.

Data retention on device

• Today + next-day tasks on the device.
• Completed events kept for 7 days post-sync for audit.
• Sensitive data (customer PII) cleared on logout.

Storage + battery

Apps optimised for:

• < 200MB install size.
• Minimal background CPU.
• Battery-aware sync cadence (less frequent on low battery).

Photos + signatures

Large attachments (photos, signatures) upload opportunistically on Wi-Fi where possible, cellular otherwise. Small compressed thumbnails sync immediately; full-resolution async. Server stores both.

Failure modes

• App kill / reboot — local queue preserved.
• Wrong time on device — server rewrites to server-time on receipt, keeps device-time as metadata.
• Version mismatch — app warns and prompts update; can still sync pending events.

Security

Local data encrypted with platform keychain. PIN / biometric re-unlock required after inactivity. Stolen device: remote-wipe via admin console.