When integrating Stripe into a ReactJS application for selling digital products, experienced developers should consider several lesser-known challenges, pitfalls, tips, and tricks to ensure fault tolerance, flexible/maintainable code, modern UIs, data security, efficient data storage and retrieval, and a great user experience. Here are some specific examples:

1. Fault Tolerance:

   • Implement robust error handling and retry mechanisms when making API calls to Stripe. Use libraries like Axios or Fetch with built-in retry functionality to handle network failures gracefully.
   • Utilize Stripe's idempotency keys to prevent duplicate charges in case of network issues or accidental multiple submissions.
   • Implement a circuit breaker pattern to prevent cascading failures and limit the impact of Stripe API outages on your application.

2. Flexible/Maintainable Code:

   • Use a modular architecture and separate concerns by creating dedicated services or modules for Stripe-related functionality, such as payment processing, subscription management, and webhook handling.
   • Leverage dependency injection to make your code more testable and maintainable. Use libraries like InversifyJS or Angular's dependency injection system.
   • Utilize Stripe's API versioning and upgrade your integration regularly to take advantage of new features and improvements.

3. Modern UIs:

   • Implement a smooth and intuitive checkout experience using Stripe Elements, which provides pre-built UI components for collecting payment information.
   • Customize the appearance of Stripe Elements to match your application's branding and design system.
   • Use Stripe's Payment Request API to enable express checkouts and support digital wallets like Apple Pay and Google Pay.

4. Data Security:

   • Never store sensitive payment information, such as credit card numbers, on your server. Utilize Stripe's tokenization process to securely transmit payment data.
   • Implement proper authentication and authorization mechanisms to protect user data and prevent unauthorized access to Stripe-related endpoints.
   • Enable Stripe's Radar fraud detection system to identify and prevent fraudulent transactions.

5. Storing and Retrieving Data:

   • Use Stripe's Customers API to store customer information securely and associate it with payment methods for future transactions.
   • Implement efficient data synchronization between your application's database and Stripe's records. Use Stripe's webhooks to receive real-time notifications about events like successful payments, subscription updates, or refunds.
   • Utilize Stripe's metadata feature to store additional data associated with payments, customers, or subscriptions for easier querying and reporting.

6. Great User Experience:

   • Implement real-time payment status updates using Stripe's webhooks to keep users informed about the progress of their transactions.
   • Handle payment failures gracefully by providing clear error messages and guidance on how to resolve issues, such as updating expired card information.
   • Offer a seamless subscription management experience by allowing users to easily upgrade, downgrade, or cancel their subscriptions through a self-service portal.

7. Testing and Debugging:

   • Use Stripe's test mode and test API keys during development and testing to avoid making actual charges.
   • Implement comprehensive unit tests and integration tests to verify the correctness of your Stripe integration. Use libraries like Jest or Mocha for testing ReactJS components and Stripe-related functionality.
   • Utilize Stripe's webhook signing and verification process to ensure the authenticity of incoming webhook events and prevent fraudulent requests.

Remember to always refer to Stripe's documentation and best practices to ensure a secure and reliable integration. Additionally, keep your Stripe integration up to date with the latest API versions and security patches to maintain a high level of security and compatibility.