Bidirectional Shopify API Integration

I need a solid connector that keeps my Shopify store and our custom backend completely in-sync in both directions. Inventory counts, new or updated products, incoming orders and the related customer records must travel flawlessly between the two systems in near real-time, with updates flowing back to Shopify just as reliably.

My backend is fully custom, so the job involves working directly with the Shopify Admin REST and/or GraphQL APIs, setting up the necessary webhooks, and writing clear endpoints or workers on our side.
Deliverables (all required for hand-off):

• Clean, well-documented code that pushes and pulls product, inventory, order and customer data bidirectionally
• Webhook and scheduler setup that guarantees no data loss, even on high-volume days
• Field-mapping documentation so my internal team can maintain or extend the integration later
• Basic test script or Postman collection proving typical use-cases succeed (product creation, stock change, order status update, customer edit)

When everything is done I’ll validate by running live syncs in a staging store; if each data type reflects correctly in both systems within the agreed interval and logs show no errors, the project is complete.