Help Needed: Building Custom App Outside Shopify (React + FastAPI) and Integrating with Shopify Based on Detailed Workflow

Shopify Flow
1

Hi Shopify Community,

I’m planning to use Shopify as the main e-commerce platform for my project, but I want to build a custom full-stack application (React frontend + FastAPI backend) outside of Shopify for more control over user registration, inquiries, and customer service processes. My goal is to integrate this custom app with Shopify to manage products, orders, and customer interactions.

Here’s a high-level workflow I want to implement:
Customer Journey:

  • Customer lands on site (React frontend)
  • Choose to Register/Login/Proceed without registering
  • Registration form includes custom fields like Company Name, GST No.
  • Email verification step
  • Product viewing and inquiry system (some can proceed without logging in)
  • Inquiries go to SME, tracked in the backend
  • Email notifications to SME and Customer
    SME Journey:
  • SME gets inquiry
  • Follows up with customer
  • Finalizes orders
  • Tracks proposal, PO, order status, fulfillment, delivery
  • Sends proposals via email
  • Installation and feedback tracking
  • Payment process (prepaid/postpaid tracking)
    Admin Panel:
  • Add/modify/delete products (sync with Shopify)
  • Design custom inquiry forms
  • Track metrics (orders, tickets, low stock)
  • Manage users and roles
  • Handle customer tickets
    Customer Support:
  • Ticketing system for customers via dashboard
  • SME and care team resolution workflows

What I Need Help With:

  1. Can I build this custom workflow in an external app (React + FastAPI) and connect it to Shopify?
  2. Which Shopify APIs or App Bridge features would be best to use for product sync, customer handling, order tracking, etc.?
  3. Can my app handle registration, inquiries, and ticketing externally but still use Shopify for order and inventory management?
  4. Best practices for authentication between Shopify and my custom app?
  5. Any example apps or architecture you can recommend for this hybrid setup?

I really want to use Shopify’s power for commerce but keep my own workflow logic externally.

Payal

2

This isn’t a Flow question…you might have better luck posting in another topic.

3

Thanks for pointing that out! You’re right this probably doesn’t belong in the Flow section. Could you please suggest which topic or section would be the most appropriate for questions about integrating a custom app (React + FastAPI) with Shopify’s APIs for product and order management? I’ll repost it there. Appreciate your guidance!

4

That’s a broad topic, so I would post in the “partner discussion” but you’ll have better success asking smaller specific questions