Optimizing Checkout Logic with Shopify Functions

For years, `checkout.liquid` was the only way to customize the Shopify Plus checkout. It was powerful, but risky—one bad line of code could break your revenue stream. Shopify has now deprecated `checkout.liquid` in favor of Shopify Checkout Extensibility and Shopify Functions. This is a massive upgrade for stability and performance.

What are Shopify Functions?

Functions allow developers to write backend logic (often in Rust or JavaScript) that is injected into Shopify's backend flow. Unlike apps that host logic on their own slow servers, Functions run on Shopify's infrastructure, meaning they run in under 5ms.

Use Case 1: Advanced Discounting

You can build complex bundle logic that standard Shopify discounts can't handle. For example: "Buy a coffee maker, get 50% off filters, but only if the customer has tagged 'VIP'."

Use Case 2: Delivery Customization

You can hide or reorder shipping methods dynamically. If a cart contains a "Hazardous Material" product, a Function can instantly hide "Express Air Shipping" from the options, preventing compliance issues.

Use Case 3: Payment Gateway Logic

You can reorder payment methods based on order value to save on fees. For extremely high-value orders, you might hide credit card options (high fees) and only show Bank Transfer options. Or, hide "Cash on Delivery" for customers with a history of returns.

Transitioning from `checkout.liquid` is mandatory. Ogray Design specializes in refactoring legacy checkout code into modern, app-based extensions.