Glossary
Master and replica
LAN POS · local server POS · paired devices
In a master-and-replica POS, one device in the venue, the master, holds the data and serves every other terminal, kitchen screen and display over the venue's own local network, and each of those replicas keeps a copy it can read when the master is briefly unreachable.
One owner of the data
Every command, such as adding an item or taking a payment, goes to the master, which validates it, records it and tells every replica. There is one order of events and one place that decides it, which is what keeps two terminals from both selling the last portion.
Replicas catch up, not merge
A replica that loses the master keeps showing what it knows and queues what it did. When the connection returns it replays the events it missed and lands its own. Nothing is merged by hand and nothing is lost.
The network is yours
The devices talk over the venue's own LAN or Wi-Fi. The internet is not in the path. A router reboot pauses the replicas for a moment; a dead ISP does nothing at all. If the master fails, another device is promoted to master by a deliberate act.
How Brindola does it
The master runs the venue's server and database; terminals, kitchen screens and guest displays pair to it over the LAN. Promotion is manual and recorded. Printers, terminals and fiscal devices belong to a named device or to the master role, so hardware follows a promotion.