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Build a POS that survives the internet · part 1

Offline-first POS, part 1: why the network cannot be on the critical path

Most POS demos assume a working connection. Real shops do not have one. The architecture that keeps a till selling through an outage — and why offline-first is an ordering decision, not a feature.

10 Aug 20265 min read8 views

Tutorials

Build a POS that survives the internet · part 2

Offline-first POS, part 2: never store a stock level

The schema decision that makes offline sync work: store append-only stock movements and derive the level, so two tills syncing in either order reach the same answer.

10 Aug 20264 min read3 views

Tutorials

Build a POS that survives the internet · part 4

Offline-first POS, part 4: idempotent sync and the last-item problem

Accepting a batch that contains sales you already have, per-sale transactions so one bad record cannot poison a batch, and what to do when two tills sold the same last item.

10 Aug 20263 min read4 views