Senior Shopify Full-Stack Developer / API Integration Engineer

We operate an existing Shopify-based custom printing business and are looking for a senior developer to help build a lightweight custom fulfillment experience on top of our current store. This is not a theme-only role. We need someone comfortable with Shopify custom development, third-party API integrations, webhooks, lightweight backend services, and preserving a clean architecture for future expansion. The selected developer will act as the technical owner of the first phase and work with a frontend developer. The project involves: Shopify integration Custom fulfillment logic External API integration Order metadata/session persistence Lightweight backend or middleware where necessary Working with existing third-party fulfillment/order-management tools Preparing the architecture for a more advanced custom ordering experience in a later phase We will provide the full technical scope and workflow only to shortlisted candidates. Required skills: Shopify custom apps, Shopify Admin API, webhooks, JavaScript/TypeScript, Node.js, REST APIs, third-party integrations, Git/GitHub. Preferred: experience with fulfillment, delivery/logistics APIs, middleware, order-routing systems, and scalable e-commerce architecture.