Case study
Interesim.
A travel-eSIM marketplace: buy a data plan for anywhere in the world, scan a QR code, land connected — no roaming fees, no airport SIM kiosks.
- Role
- Solo engineer — design to release
- Platform
- iOS & Android
- Stack
- React Native · Expo · Supabase · TypeScript
- Year
- 2025 — 2026
From zero
Interesim started from a familiar pain: landing in another country and paying absurd roaming fees, or hunting for a SIM kiosk at the airport. The idea — buy a data plan before you fly, scan a QR code, land connected.
I built it alone, end to end. The catalog, ordering and eSIM provisioning run through a wholesale eSIM partner integrated behind Supabase Edge Functions, so API keys and pricing logic never touch the client. The app itself is React Native with Expo — one codebase for iOS and Android — with Zustand for state and Supabase for auth, database and storage.
The parts that took real care are invisible: keeping prices consistent across three currencies, making OAuth work across four providers plus guest mode, and designing a checkout that can mix wallet balance with card payments without confusing anyone. Every screen exists in eleven languages.
What it does
Plan marketplace
Browse data plans for individual countries or whole regions — Europe, Asia, Balkans, CIS — with live pricing, discount campaigns and multi-currency display (USD, EUR, TRY).
Full authentication suite
Email, Google, X and Facebook sign-in plus a guest mode, all running on Supabase Auth with per-provider OAuth flows.
Checkout & wallet
A price-breakdown checkout with promo discounts, card payments and Intercash — an in-app balance you can top up and spend across purchases.
eSIM delivery & install
Purchased eSIMs arrive with a QR-code install flow and step-by-step guidance, including a compatibility check before buying.
Usage tracking
Active, pending and expired eSIMs with data-usage rings, remaining/total breakdowns and plan status at a glance.
Referral program
Personal referral codes with copy/share actions, earnings tracking, and wallet credit for both sides.
11 languages
Full localization from Turkish and English to Arabic and Russian — switchable in-app, remembered per account.
Inside the app
Under the hood
- React Native + Expo — one TypeScript codebase for iOS and Android, expo-router navigation, Zustand state.
- Supabase backend — Auth (email, Google, X, Facebook, guest), Postgres, storage.
- Edge Functions — the wholesale eSIM partner API lives server-side: catalog sync, order placement and provisioning, with keys and pricing logic never shipped to the client.
- Design system — custom components, dark brand palette, reanimated micro-interactions, SVG iconography throughout.