Cross Platform Mobile App Developer for Building an Exam Prep App

We are looking for a talented, detail-oriented Freelance Mobile Application Developer to build a cross-platform (iOS & Android), offline-first exam preparation app designed for industrial professionals studying for rigorous technical certifications. This is an application featuring quiz engines, spaced-repetition flashcards, dynamic performance analytics, and a tiered monetization structure (Free, Basic, and Pro tiers). The ideal candidate has deep experience handling offline database synchronization, secure local storage, micro-transactions, and highly responsive custom UI components optimized for field environments. Key Responsibilities Cross-Platform Architecture: Develop, test, and deploy a high-performance app for iOS and Android. Offline-First Database Design: Implement a robust local storage architecture to store thousands of engineering questions, flashcards, images, and user progress locally. Ensure seamless background syncing when network connectivity is restored. Custom Interface Engineering: Build a thumb-ergonomic, high-contrast user interface optimized for high-glare industrial field environments. Quiz & Security Mechanics: Program custom quiz parameters, including strict text-selection/clipboard lockout, native countdown timers, manual reference PDF navigation trees, and conditional feedback states based on user tiers. In-App Purchases & Monetization: Implement multi-tier gatekeeping logic (Free vs. Basic vs. Pro) utilizing App Store and Google Play in-app purchases or Stripe subscription integration. Analytics & Integration: Connect the app via REST APIs to a centralized backend or LMS (Moodle/Airtable webhook ecosystem) to seamlessly unlock premium Pro video course components. Required Technical Skills Frameworks: 5+ years of proven commercial experience with Flutter (Dart) or React Native (TypeScript). State Management: Mastery of scalable state management solutions (e.g., Bloc/Provider for Flutter, or Redux/Zustand for React Native). Database Systems: Extensive experience with local offline-first mobile databases (SQLite, Hive, Room, Realm) and cloud sync strategies. Security & Protection: Deep understanding of mobile security standards to prevent data scraping or text copying of copyrighted question banks. Media Handling: Experience building embedded, secure PDF rendering systems with custom controls (disabling default native search/Ctrl+F features). Respond with portfolio having examples of apps developed, specially in EXAM PREP/PROFESSIONAL TRAINING Domain