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The Essal Check-In App is designed to keep working even when the device loses internet connectivity. Employee and guest data is cached locally so that scans can be verified without a live connection.

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How Offline Mode Works

When the device is online, it continuously syncs data to a local database stored on the device:
  • On startup: a full sync downloads all employees and guest badges for your organization
  • Every 5 minutes: an incremental sync fetches any records updated since the last sync
  • Employee photos are pre-fetched in the background so they appear on result cards even offline
  • Real-time updates are received via a live database subscription when online
All sync data is stored in an on-device database (IndexedDB), keyed to your organization. Data from other organizations is never mixed in.

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Cache Freshness

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Check-In Log When Offline

Scan events are always recorded, whether the device is online or offline:
  • Every scan is saved immediately to the local database
  • When the device comes back online, pending events are automatically flushed to the server
  • Photo captures are also uploaded when connectivity is restored
No scan data is lost due to connectivity issues.

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Heartbeat and Online Status

The device sends a heartbeat signal every 2 minutes to the server while online. This updates the last seen timestamp visible in the admin panel. The device also uses the heartbeat response to check its activation status:
  • If the server reports the device has been deactivated by an admin, the app immediately shows an offline lock screen
  • The last heartbeat time is stored locally so the app can calculate how long it has been offline

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Offline Warning and Lock

The app monitors how long it has been since the last successful server connection: Warning (amber banner): Shown when the device has been offline for 2 hours less than the configured maximum (e.g., warns at 22 hours if the limit is 24 hours). The app is still fully functional. Offline lock (📡): Shown when the device exceeds the maximum offline duration (default: 24 hours). Scanning is disabled until the device reconnects. The screen shows when the device last came online and a Reconnect button to retry. Revoked lock (🚫): Shown when the admin has deactivated the device from the admin panel. This lock cannot be dismissed — the operator must sign out. To restore access, an administrator must reactivate the device from the admin panel and re-register it if necessary.

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Adjusting the Offline Limit

The maximum offline duration is configurable per device. By default it is 24 hours. To change it, edit the Max offline hours setting in the Settings tab of the check-in app. Lower values are recommended for high-security environments.