Secure Payment Processing Integration

I need to add end-to-end payments processing to my application so that customers can complete financial transactions without ever leaving the platform. The core work involves choosing and integrating a mainstream gateway (Stripe, PayPal, Adyen or a comparable API), wiring up the server-side logic, and exposing clean client-side calls that handle tokenisation, 3-D Secure flows, refunds and recurring charges where relevant.

The codebase is currently built in Node.js with a React front end, so familiarity with this stack, REST/GraphQL, and typical PCI-DSS best practices is important. I already have merchant accounts in place; what I am missing is the glue that turns an order into a confirmed, securely captured payment and stores the resulting transaction metadata in my PostgreSQL database.

Please bring experience with webhooks, idempotency keys, sandbox vs. live environment rollouts and automated test scripts that simulate edge-case payment scenarios. I value clear commit history, concise documentation and reproducible local setup instructions.

Acceptance criteria:
• A user can submit a payment from the UI and receive an immediate success or failure response.
• All sensitive card data stays with the gateway; no raw PAN is logged or stored.
• Failed transactions generate helpful error messaging and retry logic.
• Successful transactions appear in both the gateway dashboard and my internal admin panel with matching IDs.
• Unit/integration tests cover at least the happy path, declined card, expired token and network timeout cases.

Once everything passes review, I will push the changes to production, so efficient knowledge transfer and a brief walkthrough are the final steps.