I will integrate alipay or wechat pay with reconciliation and refunds

Payment APIs are easy. Everything around them is not. I have integrated Alipay, WeChat Pay and aggregators in production. What goes wrong, and what I handle by default: Idempotency. The same order gets the callback twice. Without idempotent writes you charge or grant twice. Every write path is keyed on your order id. Reconciliation. The gateway says paid, your database says pending. You get a reconciliation view, so you settle the gap now instead of during an audit. Refunds. Partial and full refunds, balance and stock rollback, visible status at every step. States are written down and built as a state machine, not scattered ifs. Callback verification. Signature checks, replay protection, and a searchable log for the day a customer insists they paid. Fraud guards. Where there is a subsidy: limits by account, phone and address. Deployment. You don't get a zip - you get it running, with database initialized and certificates in place. Send me your channels and credentials.

I have integrated Alipay, WeChat Pay and aggregators in production. What goes wrong, and what I handle by default:

Which payment methods and aggregators do you support?

Idempotency. The same