We used other payment gateways before Stripe. We built the abstraction around the requirements for our business model, although after some iterations it became

We used other payment gateways before Stripe. We built the abstraction around the requirements for our business model, although after some iterations it became similar to the model used by Stripe (customers, sources, plans...). We support saved payment options and on them we do recurring billing and one-stop payments. A user for us can have multiple sources and a source is a saved external card or payment method, in the case of Stripe a source is a combination of the Stripe customer id and Stripe source token. Most payment gateways support some kind of token that represents a saved card or similar on which you can do a charge.