Android POS Developer — Kotlin / Compose Field Payments App (Sunmi Handheld)

We are building the Android app for a field-agent payments network. Agents carry a rugged Sunmi handheld with a built-in thermal printer, take cash at a kiosk or market stall, and sell airtime, prepaid electricity and gas from their own prepaid wallet. No cards, no customer-facing app, no guaranteed internet. It is roughly 20 screens. It is not a big app, it is a hard one, and the difficulty is state and failure, not UI: - A payment can simply not answer. The money may or may not have moved, so the app has to treat “indeterminate” as a first-class outcome instead of calling it a failure. - Offline-first is a correctness requirement, not a cache. A local journal of payment intent is the source of truth for what the agent sees. - The hardware fights back: a thermal printer to drive, a low-end 2 GB device, and a fleet that may ship without Google Play Services. What is already done ------------------------- Design is finished, an annotated Figma covering every flow and every second state: error, empty, offline, loading. The backend is built with a documented HTTP API, a stable error contract, and hand-offs docs written for the app developer. You must have ------------------ - 4+ years Android, with Kotlin and Jetpack Compose in production - Deep coroutines and Flow; structured concurrency, scoping and cancellation. This is our single biggest filter. - Offline-first architecture, with Room as a source of truth - MVVM / unidirectional data flow, testable layering, injected dispatchers - REST integration against an API you did not design and you must test failure paths, not just the happy one A strong plus ---------------- - Experience building on Android POS hardware (Sunmi, or any ESC/POS or bound-service (AIDL) thermal printer integration, device identity, and sideload / MDM distribution rather than the Play Store - Fintech or payments background: you know why a “pending” payment is the interesting one - WorkManager in anger, on OEM builds that kill background work - Performance work on low-end hardware you could not simply replace Not needed: iOS, Flutter, React Native, KMP, or backend Python. There is exactly one target device and it will stay that way. Shortlisted candidates get the full technical brief and the engineering hand-off documents.