Retail connectivity fails at the worst moment—Saturday rush, storm, or ISP outage. POS software should degrade gracefully, not halt sales.
Persist carts locally with durable IDs. Retry sync with backoff and surface a clear “pending upload” state so staff trust the device.
Define conflict policy: who wins on price overrides, returns, or duplicate receipts? Ambiguity becomes a training problem and a support nightmare.
Test on flaky networks deliberately. Simulate latency and packet loss; pretty demos on gigabit Wi-Fi lie.
