Offline-First POS: Keep Selling When the Internet Drops

Internet outages should never stop a sale. NoPOS is built offline-first: the counter keeps ringing, the queue holds every transaction, and everything syncs cleanly when connectivity returns.

Queue everything locally

• Record every sale, refund, and inventory movement in a local outbox the moment it happens.
• Give each queued transaction a client-generated idempotency key so replays never double-charge.
• Stamp each entry with lane, cashier, and a monotonic sequence number for deterministic ordering.

Take payments with confidence

• Authorize cards against the last known processor config and mark offline captures for settlement review.
• Fall back to cash, gift, and store-credit tenders without changing the checkout flow.
• Show cashiers a visible offline badge with the queued count so the state is never a mystery.

Sync without surprises

1. Reconnect and push the outbox in sequence order, oldest first.
2. Confirm server acknowledgements before clearing each entry from the queue.
3. Pull fresh catalog, pricing, and tax tables immediately after the push.
4. Reconcile the day's totals against the NoPOS dashboard before close.

Use Swagger UI or OpenAPI for the current sync, idempotency, and reconciliation request shapes.