Inside the Full Stack of Internet Payment Architecture: From Checkout to Settlement

Preface

Focus on shaping yourself rather than studying others!

Internet Payment Overall Architecture

We explore the end‑to‑end payment flow using a purchase of "Three Squirrels" nuts on JD.com as an example, covering the entire macro view of China's internet payment ecosystem.

First, the user accesses an e‑commerce platform (e.g., JD).

After selecting items, the user proceeds to the JD checkout, which aggregates payment methods such as JD Pay, WeChat Pay, Cloud QuickPass, etc.

These third‑party payment methods connect to commercial bank payment channels, which forward transactions to UnionPay and NetUnion.

Finally, the transaction reaches the People's Bank of China, the top of the payment food chain.

JD Pay Architecture

The JD payment flow traverses multiple systems within seconds, illustrating the complexity of the payment chain.

Payment Architecture Analysis

A typical service platform payment architecture includes a user‑facing checkout, an order system, a transaction system, a payment processing system, and a payment channel subsystem.

After a successful payment, a settlement line processes the data through a clearing center, then to an accounting system for bookkeeping, notifies the core accounting module, and finally informs the fund platform to settle merchant payments.

Payment System Architecture

The payment system handles all transaction requests from business systems, comprising a business layer (providing payment interfaces) and a payment layer (processing real‑time fund flows, splitting and merging accounts).

Cashier

The cashier page lets users select payment channels before completing a transaction, offering a consistent experience across devices and scenarios.

Cashier Business Scenarios

Typically divided into two parts: 付款 – Users initiate payment for an order (e.g., buying a shirt on Tmall and being redirected to Alipay). 充值 – Users top up their account balance (e.g., recharging a wallet on Alipay or WeChat).

Transaction Core

The transaction system sits outside the payment core, handling business logic and converting business transactions into payment orders for the payment system.

For guaranteed transactions, the flow includes user payment success, merchant shipment, user confirming receipt, and the corresponding status updates in the payment system.

User payment succeeds, marking the transaction as paid.

User confirms receipt, marking the transaction as completed.

Member System

The member system manages accounts and relationships within the payment platform, distinguishing between personal and enterprise members.

Enterprise members can configure business parameters such as settlement cycles and payment method permissions.

Most internet companies integrate payment channels without building an independent account system.

Payment Core

The payment core provides standardized payment services, abstracting downstream clearing, accounting, and settlement, and exposing unified payment request interfaces.

Boundaries of the Payment Core

支付服务

: Wraps backend payment interfaces and supports composite payments. 支付服务流程: Defines processes for recharge, withdrawal, internal transfer, refund, etc. 支付指令: Contains all necessary information to execute a payment after order creation. 支付协议: Defines product codes and payment channel details governing the payment flow.

Accounting Core

Manages account types, records fund movements, provides accounting data, and reconciles with payment channel settlements.

Clearing Core

Maintains clearing and settlement rules, executing fund distribution according to configured policies.

Conclusion

Building a third‑party payment platform requires dozens of subsystems; payment systems are far from simple.