Shopify App Developer

We're building a customer-engagement app for Shopify brands, powered by an AI voice agent. We need a developer to build the merchant-facing Shopify app end to end. WHAT YOU'LL BUILD - The embedded Shopify app: OAuth install flow, session token auth, multi-store support - Shopify GraphQL Admin API integration (REST is legacy, GraphQL only) - Webhooks: registration, HMAC verification, retries, plus the three mandatory GDPR webhooks - The UI/UX — you design and build the merchant experience. Setup wizard, configuration screens, reporting dashboard, activity views. We have direction and reference screens, not finished designs. - Database layer for per-merchant config, state, and reporting - Integration with our backend service and third-party APIs (voice, SMS, email/CRM platforms) - Shopify Billing API — recurring subscription plus usage-based metering WHAT WE HAVE TODAY Working MVPs, not finished software. A Node backend that talks to a live Shopify dev store, a written spec, and rough reference screens. It proves the concept works. It is not production architecture and it is not accurate everywhere. We expect you to push back on it. If the data model is wrong or the structure won't scale to hundreds of merchants, say so and rebuild it properly. We would rather pay to do it right once. LANGUAGES AND TOOLS YOU NEED Languages - JavaScript / TypeScript (primary) - Node.js - React - SQL - GraphQL - HTML / CSS Shopify stack - Shopify Remix app template - Shopify App Bridge - Shopify Polaris (design system) - Shopify GraphQL Admin API - Shopify Billing API - Shopify CLI + dev stores Everything else - Postgres (or MySQL) — schema design, migrations, indexing - Redis or a job queue for scheduled/background work - REST + webhook integrations, OAuth 2.0, HMAC signing - Figma — you'll design screens before building them - Git / GitHub, PR workflow - Vercel, Fly.io, Railway, or AWS for deployment SKILLS WE'RE LOOKING FOR 1. Shopify app development — you've shipped 2+ apps. Link them. 2. API integrations — you've connected multiple third-party APIs in production and handled auth, rate limits, retries, and webhook failures without losing data. 3. Databases — you can design a multi-tenant schema from scratch and explain your indexing choices. 4. UI/UX — you can take a rough direction and produce a clean, usable interface. Not pixel-perfect artistry, but merchant-ready. Show us screens you designed, not just implemented. 5. AI / LLM work — you've built with LLM APIs (OpenAI, Anthropic, or similar): prompt engineering, structured output, tool/function calling, RAG or knowledge bases, and evaluating output quality. Fine-tuning or model training experience is a plus. 6. Judgment — you tell us when our approach is wrong instead of building it anyway. NICE TO HAVE - Shopify protected customer data approval experience - Klaviyo, Recharge, Twilio, or ElevenLabs APIs - Voice AI, telephony, or conversational AI products - Marketing automation, SMS, or retention tooling for ecommerce HOW WE WORK - Based in Europe preferred — Ukraine, Poland, Romania and the wider region are all ideal. We want 3-4 hours of daily overlap with US Eastern time. - Milestones with a working demo at each one - Async by default, one weekly call - You work on branches in our repo and open PRs - Full spec, backend docs, and dev store access on day one TO APPLY — answer these four, briefly: 1. Link 1-2 Shopify apps you built. What exactly did you do on each? 2. Show us a UI you designed yourself, not one handed to you. 3. What have you built with LLM APIs? Be specific about what it did. 4. Your realistic hours per week for the next 10 weeks. Applications that skip the questions get skipped.