Shopify Functions Development Services

Most Shopify Plus stores have Scripts that were written years ago by developers who have since left. Shero audits every active Script before starting any migration, categorizes each by replacement path (native Shopify feature, public app, or custom Function), and identifies dead logic that can be dropped entirely. Most legacy Script catalogs have at least 30 percent redundancy. The audit prevents rebuilding logic that is no longer serving a business purpose.

Shopify allowed Scripts and Functions to run simultaneously until the June 30 cutoff. Shero uses this approach for all Script migrations: deploy the Function alongside the Script, run identical carts through both, and confirm the outputs match before disabling the Script. The failure mode most agencies miss is a Function that deploys successfully but returns no discount because a required field was left out of the GraphQL input query.

B2B pricing logic stored in customer metafields (wholesale tier, account type, region) cannot be expressed through Shopify's standard Discounts admin. A custom discount Function reads the customer metafield at checkout, applies the correct pricing tier, and returns the adjusted line item prices in under 5 milliseconds. This is the most common custom Function use case for wholesale and distribution brands on Shopify Plus. It connects directly to the B2B architecture work Shero builds for these merchants.

Retail customers and wholesale accounts need different payment options at checkout. A payment customization Function reads customer tags or company account data and hides, reorders, or renames payment methods accordingly. Up to 25 payment customization Functions can run simultaneously per store, covering different customer segments and order types at the same time.

Hazmat products, PO box restrictions, carrier-specific rules for B2B accounts, and zone-based rate structures all require shipping logic that Shopify's standard shipping admin cannot express. A shipping Function receives the cart contents, delivery address, and customer data, applies the required logic, and returns the correct rates. Shero has built shipping Functions for shooting sports brands managing hazmat restrictions and for B2B distributors with carrier contracts per account type.

Custom Shopify Functions for bespoke logic must be built as private apps through the Partner Dashboard and connected to the store. Custom apps created through the Shopify admin do not support Shopify App Bridge, which Functions require. Shero builds Functions as properly structured partner apps, which means they are maintainable, testable, and deployable through Shopify CLI rather than fragile admin customizations. This is covered as part of the broader custom development practice.