Case study: the architecture of an offline-first field sales app for distributor reps, built with Expo and Supabase and in production since November 2025: offline sync queue, row-level security, roles, dates and scheduled jobs.

For the past year I've built and run the field sales system for a distributor. Every working day since November 2025, reps open it on mid-range Android phones, follow a planned list of dealer visits, check in with GPS and photos, record payments, take orders, and log their company car's odometer. Team leads plan the days, accounts staff validate payments, and directors watch every region against target.

It's an Expo (React Native) app with a Supabase backend: 64 tables, 132 database functions, 163 row-level security policies, about 55,000 lines across 86 screens. One codebase ships to iPhone, Android and a browser console.

Here's what mattered most, in the order I'd tell a team starting the same build.

1.…