domain-ecommercepayment-integration

Payment gateway integration patterns for e-commerce: Stripe, PayPal, Adyen, Square, Mollie, Razorpay, Checkout.com, BNPL (Klarna, Affirm, Afterpay), crypto payments (BitPay, BTCPay), payment orchestration (Primer, Spreedly), 3DS2 authentication, fraud prevention (Sift, Riskified), subscription billing, refunds/disputes, multi-currency, and idempotency.