Payment System: Detailed Component Design

Step 6: Detailed Component Design

The high-level design gave us the shape of the system. Now we open its key parts one at a time, and look at how each one actually works.

6.1 API endpoints

Five endpoints cover the core flow:

• POST /v1/charges creates a charge.
• GET /v1/charges/{id} returns the status of a charge.
• POST /v1/charges/{id}/refund creates a refund. A separate /v1/refunds resource also works.
• GET /v1/balance returns the merchant's current balance.
• GET /v1/transactions?filter... lists transactions, usually in pages.