Dube

Shopkeepers record credit in notebooks that get lost, can't be searched and never remind anyone to pay. Connectivity is unreliable, so a cloud-only app would fail at the counter.

The phone's SQLite database is the working store, so every action works offline. A hand-written sync engine pushes local changes and then pulls server changes using server-set cursors. Each shop is a tenant, and a subscription lock blocks writes after a grace period on both the server and the device.

• 19 end-to-end API tests cover tenant isolation, the sync contract and the subscription lock.
• A written sync protocol document defines the contract between the app and the API.
• One runbook brings up the API, admin panel and Android app with seeded demo accounts.

• Record credit and repayments with no connection
• Home screen of everyone with an outstanding balance, with tap-to-call
• English, Amharic and Afaan Oromo
• 14-day trial with offline payment by Telebirr, bank or cash, activated from the admin panel
• Writes blocked after a seven-day grace period, reads always allowed
• Money stored as whole santim end to end to avoid rounding errors

Three repositories: a NestJS API, an Expo Router app and a Vite admin panel.

• Tenant scoping applied to every query through AsyncLocalStorage context
• Push-then-pull sync with dirty flags and last-write-wins conflict handling
• Phone number and password sign-in through Better Auth
• PostgreSQL and Redis in Docker Compose, with a separate test database