Make API request when an order of my client's products is made

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Hi I'm developing an app in Shopify for a customer and my customer also has a personal website in which she sells products. I'm creating a Shopify dropshipping app for her in which the users can publish her products in their Shopify storefront and sell them. I want to know if there's a way to make API request to my API (customer website API) everytime someone purchases my client's products from any storefront that has my app installed?