Testing & Security

Why should a handler fetch the invoice from the provider's API instead of trusting the webhook body?

• Webhook bodies are always encrypted
• The webhook may be a repeat, out of order or stale, and the API gives the invoice's current state
• Fetching is faster than reading the body

What does making fulfilment idempotent mean?

• It runs only during business hours
• It retries until it succeeds
• Running it a second time for the same order changes nothing