eSIM Platform is a full-stack eSIM marketplace: a Next.js web application (marketplace, admin panel, checkout) and a companion Flutter mobile app (iOS & Android). Both share the same REST API backend and PostgreSQL database, letting travelers discover, purchase, and manage eSIM data plans on web or mobile. The web handles admin operations, eSIM provider integration, and web checkout Stripe / Lemon Squeezy); the mobile app adds native store billing (RevenueCat), Stripe, Adyen, PayPal, push notifications, and Firebase Remote Config.