A cross-platform (iOS / Android / web) point-of-sale app for electronics-retail staff to ring up sales, manage stock, and process returns, with role-based access spanning cashier through super-admin.
X-POS is the front-end of a point-of-sale system for electronics-retail staff. It runs on iOS, Android, and the web from one Expo/React Native codebase, with file-based routing, an 8-slice Redux Toolkit store, a typed service layer with JWT auth interceptors, and a swappable mock backend that lets the UI be built and demoed before the API exists.
Sole front-end author. Built the entire client: file-based navigation, an 8-slice Redux state layer, a typed API/service layer with auth interceptors, RBAC, and a swappable mock backend for backend-independent development. The backend is wired-for but not in this repo (EXPO_PUBLIC_API_URL is a placeholder; the app runs against an in-process mock adapter).
Electronics-retail checkout needs cashiers to ring up multi-item sales with line-level discounts, deduct stock atomically, and handle returns, while owners restrict who can discount, refund, or manage staff. The team also needed to build and demo the full app before the backend existed.
ChallengeCircular import deadlock — the axios layer needs the store for the token, but the store imports slices that import the services that import axios.
FixLazy injectStore(store) called once at bootstrap, plus runtime dynamic imports of the refreshToken/logoutUser thunks inside the interceptor instead of at module load.
ChallengeParallel requests all 401-ing at once would each trigger a separate token refresh (a refresh stampede).
FixA single-flight refresh guarded by an isRefreshing flag; other failed requests park in a queue, resolve with the new token, and retry automatically.