Shopify Application and Integration Development

We're a small SaaS for makers (candle/soap/craft businesses) called Makers Manager. We need a Shopify integration built. This is a focused engagement, not a build-from-scratch project: our app already exists (React + TypeScript + Supabase), and I handle most day-to-day development myself. What the integration does (this is the whole MVP): - Sales in: pull orders from each connected Shopify store into our app (webhook + a reconciliation fallback, idempotent so re-syncs never duplicate). - Products + inventory out: push product catalog and inventory levels from our app to Shopify. Our app is the source of truth for stock. When a Shopify sale comes in, we recompute stock and push the authoritative number back out. - Multi-tenant: every one of our customers connects their own Shopify store via a one-click "Connect and authorize" flow. No customer should ever have to generate an API token — this must be a proper public Shopify app using OAuth. Scope of your work: - The public Shopify app: OAuth authorization-code flow, secure per-workspace token storage (server-side only, encrypted), connect/disconnect. - Orders-in and inventory/products-out sync (GraphQL Admin API; inventorySetQuantities for per-location stock). - SKU matching, with unmatched line items surfaced for the user (never silently dropped). - Compliance to pass review: protected-customer-data request/attestation and the three mandatory GDPR webhooks (customers/data_request, customers/redact, shop/redact). - I'll build the UI and the CRUD-y pieces myself. You must have (please don't apply otherwise): - Shipped at least one public Shopify app that passed Shopify's app review. Include a link or the app name. This is the #1 requirement — I need someone who's already done the OAuth + protected-data + compliance path, not learning it here. - Real experience with the Shopify Admin GraphQL API, webhooks (HMAC verification), rate-limit/backoff, and the Inventory API (per-location levels). - Comfortable with a Postgres/Supabase backend and row-level security for multi-tenant data isolation. Nice to have: inventory/COGS domain experience; prior maker/commerce tools; Etsy or other marketplace APIs (we'll do those next). How we'll work: - Fixed-price, milestone-based. The first step is a small paid trial task (a few hours): stand up the OAuth handshake against a Shopify dev store and store a token securely. If that goes well, we do the full build in milestones. - I'm responsive and technical, so you won't be waiting on me or guessing at requirements — there's a detailed spec ready to share.