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Case study · Not documented

Forged 4x4

Some commerce rules matter too much to leave in theme JavaScript five clicks before checkout.

  • Shopify Plus
  • Checkout Extensibility
  • Shopify extension tooling
  • JavaScript / TypeScript
Discipline
Shopify Plus · Checkout Extensibility · Custom business logic
Year
Not documented
Engagement
Fixed scope
Status
Live
forged4x4.com
forged

01Context

  • Implement custom Shopify Plus checkout behavior.
  • Move critical calculations into a supported extension architecture.
  • Preserve a reliable customer purchasing experience.

Forged 4x4 required advanced purchasing logic beyond ordinary theme customization.

The behavior affected checkout-level calculations, making Shopify Plus extensibility the appropriate layer rather than relying on storefront hacks.

HeapByte implemented custom checkout functionality designed to work with Shopify's controlled extension architecture.

02What was in the way

  1. 01

    Checkout restrictions

    Shopify intentionally limits arbitrary checkout code, requiring platform-supported extension patterns.

  2. 02

    Business-critical calculations

    Incorrect logic at checkout can directly affect order values and customer trust.

  3. 03

    Upgrade safety

    The solution needed to avoid dependencies on deprecated checkout modifications.

03Architecture

What we built, and what we deliberately left alone.

  1. 01

    Checkout extension

    Custom UX and logic are implemented through Shopify's supported checkout extensibility model.

  2. 02

    Server-side business rules

    Critical calculations are separated from ordinary storefront presentation where appropriate.

  3. 03

    Platform-native integration

    The implementation follows Shopify Plus extension boundaries rather than modifying inaccessible checkout internals.

FIGMA / DESIGNERP · NETSUITECRM · KLAVIYOHEAPBYTE LAYERSTOREFRONT / THEMECHECKOUT EXTENSIONSSHOPIFY FUNCTIONS

Delivery

  1. Rule discovery
  2. Extension architecture
  3. Calculation implementation
  4. Checkout QA
  5. Production rollout

04Outcome

Platform
Shopify Plus

Checkout-specific customization delivered

Architecture
Extensible

Avoids fragile legacy checkout modification

Business logic
Custom

Store-specific calculations integrated into purchasing

05Engineering notes

Extension isolation
Checkout components operate within Shopify's sandboxed extension environment.
Business-rule validation
Custom calculation inputs are validated before influencing checkout behavior.
Upgrade resilience
The architecture avoids reliance on legacy checkout template modifications.
Shopify Plus context
The solution takes advantage of Plus-specific extension capabilities unavailable in standard theme code.

What we took from it

  1. 01Checkout logic should use Shopify's supported extension boundaries.
  2. 02Business-critical calculations need stronger validation than ordinary UI features.
  3. 03Theme code and checkout code have very different lifecycle constraints.
  4. 04Platform-native extensibility is more maintainable than legacy injection techniques.

Disciplines applied

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