Learn how to quickly determine whether Shopify Functions are the right solution for a merchant's checkout customization, and when to use JavaScript or Rust to build it. This video walks through a practical decision tree you can use when planning solutions to assess whether the need truly belongs at checkout, how complex the business logic is, and whether it involves heavy computation. You'll learn when a simple JavaScript Function or tools like Shopify Flow are sufficient, when Rust is needed to meet performance constraints, and when a custom app or set of webhooks is a better fit than Functions at all.