> ## Documentation Index
> Fetch the complete documentation index at: https://docs.billions.works/llms.txt
> Use this file to discover all available pages before exploring further.

# Go-live checklist

> Verify reliability and security before accepting production payments.

## Configuration

* [ ] Production API credentials are stored in secret storage.
* [ ] The production API host and version are configured.
* [ ] The callback URL is public and uses HTTPS.
* [ ] No credentials or sensitive payloads are written to logs.

## Payment behavior

* [ ] Invoice creation uses a stable `order_no`.
* [ ] Every logical create attempt has an idempotency key.
* [ ] The Billions invoice ID is stored with the order.
* [ ] Customers are redirected using the returned `invoice_url`.
* [ ] Expired and failed invoices can be retried intentionally.

## Verification and reliability

* [ ] Callback fields are not trusted as proof of payment.
* [ ] Invoice state is retrieved from the authenticated API.
* [ ] Duplicate callbacks do not duplicate fulfillment.
* [ ] Network timeouts and temporary failures are retried safely.
* [ ] Monitoring alerts on repeated callback or API failures.

## Test cases

* [ ] Successful payment
* [ ] Abandoned checkout
* [ ] Expired invoice
* [ ] Duplicate callback
* [ ] Callback arriving before the customer returns
* [ ] Delayed payment confirmation
* [ ] API timeout during invoice creation
* [ ] API timeout during callback verification

<Note>
  TODO: Add production support contacts, status page, rate limits, and the
  environment-switching procedure.
</Note>