Best practices for usage-based billing on embedded Shopify app

Technical Q&A
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Hi everyone,

I’m building an embedded Shopify app that acts as an affiliate marketplace. Merchants connect their store, their products are displayed on our marketplace, and when a customer clicks “Buy”, they’re redirected to the merchant’s Shopify store via a cart permalink with a storefront access token.

I want to charge a 5% commission on sales attributed to my app.

My current implementation plan:

  1. Billing setup: Use appSubscriptionCreate with usagePricingDetails
  2. Order attribution: Use storefront access token + cart permalink so orders have my app as the source/sales channel
  3. Charging commissions: Call appUsageRecordCreate for each order attributed to my app
  4. Order detection:
    • orders/paid webhook, filter by source_name

My questions:

  1. Is this the right approach for usage-based affiliate commissions? Or is there a better pattern?
  2. Order attribution: How do I reliably detect that an order came from my app? I’m using cart permalinks
  3. Billing flow UX: After appSubscriptionCreate, I redirect to the confirmationUrl using
    window.top.location.href (App Bridge v4).
  4. When to create the subscription?
  5. Webhook vs Polling ?