E-commerce Payment Gateway

GSI Commerce — later acquired by eBay Enterprise — ran the e-commerce backbone for a long list of European retail brands. Their payment gateway was the part of the stack that absolutely could not break, and the part that needed to keep evolving as new payment methods, currencies, and fraud patterns landed in the EU.

My work was inside the gateway itself: enhancements to the transaction flow, integrations with new processors and banks across Europe, and the test discipline required to ship into a system carrying real revenue every minute of the day. An early lesson in what 'mission-critical' actually means at a payments layer.