Spell & Sell
Spell & Sell
Spell & Sell
Spell & Sell
November 25, 2025
+30% AOV Lift
Real Time Pricing

Engineering the "Flex Builder" for Custom Commerce

In the world of headless commerce and advanced Shopify storefronts, the standard "Add to Cart" flow is often too rigid for high-ticket lifestyle brands. Enter the Flex Builder, a dynamic product configurator that allows users to compose their own bundles (like the cookware sets at Olavson) while unlocking progressive discounts.

From a technical perspective, this isn't just a product page; it is a mini single-page application (SPA) living within the storefront. Here is a breakdown of how a feature like this is typically architected.

The State Machine

At its core, the Flex Builder relies on a client-side state container.

This state tracks three critical distinct layers:

  • Selection Array: A list of active SKUs selected by the user.
  • Constraint Logic: Validation rules (e.g., “User must select at least 1 pan and 1 pot” or “Maximum of 5 items”).
  • Tier Status: A computed value that monitors the total value or quantity against defined thresholds to trigger discount tiers.

Dynamic Pricing Engine

Unlike standard pages where price is static, the Flex Builder requires a real-time pricing engine. As the user toggles items, the frontend must instantly recalculate:

  • Base Price: The sum of all individual SKUs.
  • Bundle Delta: The difference between the base price and the current tier's discount.
  • Visual Feedback: Updating the progress bar UI to gamify the experience (e.g., "Add one more item to save 15%").
  • Using the power of Shopify functions to calculate everything down to a milisecond

Why It Wins

For the user, it is a seamless drag-and-drop experience. For the brand, it is a conversion engine. By engineering a system that strictly couples inventory selection with dynamic incentives, brands typically see a 20-30% lift in Average Order Value (AOV) compared to static bundle pages.

See it here

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