How to handle millions of Items with tens of thousands of product categories?

3 0 1

I've learned that the number of Items we are selling: 1 million now and building to 10 or 20 million, exceeds Shopify Collections limits. I'm looking for a developer who has overcome Shopify's Collection limits and was still able to publish and automate 10s-of-thousands of parent-child relationships that make up the navigation menus.   The store is integrated with my Filemaker database via PHP.