Friday, December 18, 2020

Stripe’s Payments APIs: the First Ten Years

Michelle Bu (via Patrick McKenzie):

It’s unlikely that a developer believed a production-ready payments integration involved literally only seven lines of code. But taking something as complex as credit card processing and reducing the integration to only a few lines of code that, when run, immediately returns a successful Charge object is really quite magical.

Abstracting away the complexity of payments has driven the evolution of our APIs over the last decade. This post provides the context, inflection points, and conceptual frameworks behind our API design.

[…]

Some Sources—like cards and bank accounts—are synchronously chargeable and can be charged immediately on the server after the payment form is submitted, while others are asynchronous and can only be charged hours or days later. Users often built parallel integrations using both synchronous HTTP requests and event-driven webhook handlers to support each type. This means users now have multiple places where they’re creating a Charge and fulfilling their order. The code branching factor deepens for payment methods like OXXO, where the customer prints out a physical voucher and brings it to an OXXO store to pay for it in cash. Money is paid entirely out-of-band, making our best practice recommendation of listening for the source.chargeable webhook event absolutely required for these payment methods. Finally, users must track both the Charge ID and Source ID for each order. If two Sources become chargeable for the same order (e.g., the customer decides to switch their payment method mid-payment) they can ensure they don’t double-charge for the order.

[…]

We ended up with two new concepts: PaymentIntents and PaymentMethods. By packaging these two concepts, we finally managed to create a single integration for all payment methods.

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