Shopify Architecture Blueprint Needed

I run four in-store Shopify POS terminals plus a single Shopify Online Store and I’m ready to tighten the way everything talks to each other. My top priority is improved inventory management: every sale on any register or on the website must instantly reflect across all locations with no lag, no overselling, and no manual counts at the end of the day.

Here’s what I’m after:
• A clear, scalable architecture plan that puts a centralized inventory database at the core of the ecosystem.
• Real-time stock update workflows spelled out step-by-step, including the touchpoints for the four POS devices and the online storefront.
• Technology and app recommendations—whether native Shopify features, proven third-party apps, or custom API work—showing how they’ll slot into the architecture and why.
• A visual diagram (Lucidchart, Figma, or similar) plus concise documentation I can hand to my tech team for implementation.

Acceptance criteria
1. Every SKU change in one channel propagates to the other four channels in under one minute in your proposed design.
2. The solution must respect Shopify’s API rate limits and outline fallback handling.
3. All key data flows, fail-safes, and user roles are mapped out clearly.

If you have hands-on experience building centralized inventory solutions for multi-POS Shopify setups, I’d love to review a short outline of your approach and a sample architecture you’ve delivered before.