Virtual card issuance looks like the main feature. In production, the difficult part is accounting.
A reliable implementation separates wallet balance, funds locked to cards, issuer-reported card balance, pending authorizations, fees, and refundable amounts. Combining them into one number creates confusing dashboards and dangerous refund paths.
Three rules prevented most failures in our implementation:
- calculate percentage fees with integer basis points
- make provider transaction IDs idempotent
- roll back both principal and service fee when a top-up submission fails
We also keep read-only card-detail access free. Revealing an authenticated card number is not a network movement and should not be charged like an authorization.
This describes our work at ChinaWHAPI. Product page and published fees: https://chinawhapi.com/vcard
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