Adyen Payment API Integration

I need someone who can jump in on a part-time basis and wire our application to Adyen’s payment gateway API so we can reliably process transactions. The focus is purely on payment functionality—no social or data-sync work is involved.

Your task is to build a clean, secure integration that covers card authorisation, capture, refunds, and webhook handling for settlement events. I already have an Adyen merchant account and sandbox keys ready; you’ll plug these into our existing back-end (Node.js with Express) and make sure each payment flow is fully tested.

Please follow Adyen’s latest docs, use their client libraries where sensible, and write concise in-line comments plus a short README so the hand-off is painless. The work will be staged over a few evenings or weekends, so clear git commits and the ability to jump on a quick call for walkthroughs are important.

Acceptance criteria:
• Successful card payment, refund, and webhook test in Adyen sandbox
• All sensitive data kept off our servers (tokenisation in place)
• Error handling returns clear JSON responses to the front end
• README explaining environment variables, build steps, and test commands

If you’ve shipped Adyen or similar payment integrations before, I’d love to see a code snippet or brief example.