Shopify API Webhook Integration with Saas app built in react/typescript/express.js

I need to wire my SaaS platform directly into Shopify’s GraphQL API and event-driven webhooks so that every change to a customer record—purchase history, personal details, or on-site behaviour—appears in my app the moment it happens. The goal is friction-free customer data management: whenever a shopper makes a purchase, edits a profile field, or triggers any activity I choose to track, the data should flow into my system in real time without polling.

Here’s what the finished job looks like to me:
• GraphQL queries and mutations established for the full customer object, mapped cleanly into my existing data model.
• Subscriptions to the relevant customer webhooks (customers/create, customers/update, orders/create, etc.) set up, verified, and secured with HMAC.
• A webhook endpoint in my app that receives, validates, and persists the payload—deduplicating where necessary and handling retries gracefully.
• Real-time propagation confirmed by a test plan that proves all three data points (purchase history, personal details, behaviour/activity tracking) update almost instantly in the UI.
• Brief, clear documentation so my team can extend the integration later.

The stack on my side is flexible; if you are equally comfortable with react/typescript/express.js and can demonstrate prior Shopify GraphQL + webhook work, we’ll get along fine. Robust error handling, low latency, and clean, maintainable code are the must-haves.

You will need to share live examples or code snippets where you have implemented this for proof of work