Ask HN: Building KasirCepat, an offline-first POS for Indonesia

I'm building KasirCepat, a POS application for small shops in Indonesia. Many of these businesses have unreliable internet connections, so I started with a local-first architecture instead of cloud-first. The main goal is to make the daily workflow simple: - selling products, - tracking inventory, - viewing sales history. I'm curious how other developers approach: - data synchronization, - multi-device workflows, - handling conflicts, - designing software for non-technical users. Especially interested in lessons from building local-first/offline-first applications.