Shopify cart and promotions rebuild for a campaign

Problem

Nine days before a major seasonal campaign, the client's Shopify promotions stack was broken: add-to-cart produced quantities of zero, the cart sidebar flickered, and discount thresholds were hardcoded in one currency and failed in others. The client needed a reliable cart in time to brief affiliates.

Solution

Rather than patch a compromised installation, the senior Shopify team diagnosed the codebase, duplicated the stable live theme, and reinstalled the discount app from scratch on a clean base, first stripping the losing variant of a live A/B cart test so work happened only against the winning path. The team worked through the app's client-side API so dynamic pricing rendered across cart, product and collection pages and checkout, built a discount bar showing original versus discounted price, and, when the app's free-gift progress bar proved unreliable, removed it and rebuilt it from scratch with a dynamic free-delivery threshold. Screen-share debugging separated environment-specific issues from real defects.

Key features

• Clean-slate reinstallation of the discount app on a duplicated stable theme
• Hand-built free-gift cart progress bar with increment and decrement logic
• Discount bar showing original and discounted price after a voucher is applied
• Fix for add-to-cart re-render/flicker and zero-quantity defects
• Dynamic pricing across cart, product, collection pages and checkout
• Dynamic free-delivery threshold handling
• Currency-aware discount thresholds replacing hardcoded values

Tech stack

• AJAX cart
• CSS
• Discount Ninja
• JavaScript
• Shopify
• Shopify automatic discounts