Cross-Platform Mobile App Development

I need a skilled mobile app developer to create an e-commerce app for both iOS and Android platforms. The app should include:

- User authentication
- Push notifications
- In-app purchases

Ideal candidates should have experience with:

- Cross-platform development frameworks (e.g., React Native, Flutter)
- Secure user authentication protocols
- Implementing push notification services
- Setting up in-app purchase systems

Please provide a portfolio showcasing similar projects.