We replatformed PetHQ to Shopify Plus, engineering a custom Autoship engine and heavy-freight logic to protect margins on bulk food orders. Scope: Replatform to Shopify Plus, Custom Subscription App, Freight API. Measurable outcomes: +40% Retention (Autoship); 30% Shipping Margin Recovery. Timeframe: Within 90 days post-launch. Attribution: YoY comparison after legacy migration.