International payment gateways: what they all share

PayPal, EMS, Paysafe, Stripe, Mollie, Pay.nl and Ogone look very different, but each does the same few things: it starts a payment, sends the customer back, and reports the result.

One contract

The system worked against one contract, and each gateway was an adapter. Adding a gateway meant writing an adapter, never touching the payment flow.

Do not trust the return, ask

A customer coming back to the site is no proof of payment. The final status was always asked of the gateway itself, a principle SimaCMS’s wallet keeps today.