Adding Payments to a Small App Without Building a Billing System
Accepting money sounds like the kind of feature where I should build a large billing system.
For most small applications, I really do not want to.
A payment provider can already handle the difficult parts: card processing, checkout, receipts, taxes in some setups, subscription management and a lot of the security requirements I would rather not implement myself.
My application mainly needs to know three things:
- what the user is buying;
- whether the payment succeeded;
- what access or balance should change afterwards.
A typical flow can be quite small:
user chooses a product
↓
backend creates checkout
↓
payment provider handles payment
↓
webhook confirms the result
↓
application updates the user's access
The important detail is that I do not want to trust the browser simply because it returns from a “success” page.
The reliable confirmation should come from the payment provider, usually through a webhook. That gives the backend a trusted event it can use to update the user’s subscription, credits or purchased product.
This also means I can avoid storing card details entirely. The provider owns that problem.
There is still product logic I need to design myself. What happens after a refund? What if a webhook arrives twice? Does a subscription unlock features or add usage credits? What happens when payment fails?
But those are problems specific to my application, which is exactly where I want to spend my time.
The goal is not to build billing infrastructure. The goal is to add payments to the product with as little custom billing infrastructure as possible.
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