Selling offline and syncing
CEMAC POS works with no connection. Sales queue on the device and upload themselves safely once you are back online.
Networks in the region are not always reliable, and a till that stops when the bars disappear costs you sales. CEMAC POS is offline-first: the app holds everything it needs on the device, so you keep ringing up customers whether the internet is there or not.
How it works
Every sale is saved on the device the instant you complete it, with its own unique identity created right there on the phone. When there is no connection, sales wait in an outbox. As soon as a connection returns, the app pushes the queued sales up to the server on its own — no button to remember.
The important part is that syncing never double-counts. Each sale carries the unique id minted on the device, and the server accepts that id only once. If a flaky connection makes the app resend a sale, the server recognises the id it already has and ignores the repeat. So one real sale is always exactly one sale on the server, no matter how many times the phone retries.
Sell offline Connection returns Server | | | sale saved ---> waits in outbox ---> pushed once (unique id) (repeat id ignored)
- Sales are append-only — recorded, never quietly rewritten.
- The outbox holds anything not yet uploaded and drains automatically.
- Duplicates are impossible because the device-minted id is accepted once.
Selling through an outage
- Keep selling as normal — the offline indicator simply shows you are not connected.
- Complete each sale as usual; it is saved on the device immediately.
- Watch the outbox count rise as sales queue up. Nothing is lost.
- When the connection returns, leave the app open a moment; the queue uploads on its own.
- Check that the outbox reaches zero to confirm everything reached the server.
Do not reinstall the app or clear its data while the outbox still has sales waiting — those sales live on the device until they upload. Get back online and let the outbox empty first.
Common errors and how to fix them
| Message / symptom | Cause | Fix |
|---|---|---|
| Outbox count will not go down | No real connection yet, even if Wi-Fi shows connected. | Open any web page to test the link; once real internet is back, the outbox drains. |
| Worried a sale uploaded twice | The app retried after a dropped connection. | No action needed — the server accepts each device id once, so retries never duplicate. |
| Sale missing on another device | That sale has not synced yet from the device that made it. | Bring the selling device online so its outbox uploads; the sale then appears everywhere. |
| Prices or products look stale offline | Catalogue changes made elsewhere have not reached this device. | Reconnect and refresh; the latest catalogue downloads once online. |
| App warns of unsynced data on sign-out | The outbox is not empty. | Stay signed in and online until the outbox reaches zero, then sign out. |
Common questions
Will I ever lose a sale offline?
No. Each sale is written to the device the moment it completes and stays there until the server confirms it.
How long can I stay offline?
As long as you need. The outbox holds your sales and uploads them whenever a connection next returns.
Can two cashiers sell offline at once?
Yes. Each device queues its own sales and, because ids are unique per device, they merge cleanly with no clashes.
Try it in your own shop
Start a free 30-day trial and follow along — no card required.
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