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Before integrating, prepare the following:
  • A Billions API key stored only on your backend.
  • A public HTTPS callback endpoint.
  • A unique order reference in your system.
  • A persistent place to store the Billions invoice ID.
  • A strategy for retrying network requests safely.
The SDKs use https://api.billions.works and public API version v1 by default.

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Keep credentials server-side

Never embed the API key in browser code, a mobile application, a public repository, or logs. Load it from a secret manager or environment variable.

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Define two identifiers

Use separate identifiers for separate jobs: An order may have more than one payment attempt. In that case, keep order_no stable and use a new idempotency key for each intentional attempt.
Reuse an idempotency key only when retrying the same logical invoice creation. Do not reuse one key for unrelated orders.

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Information still required

TODO: Add the dashboard URL, instructions for creating an API key, available environments, and the definitive list of supported invoice currencies.