Full-Stack Developer (Next.js, React Native/Expo, PostgreSQL, Shopify API) for Fundraising Platform

Overview We are an early-stage company building a fundraising platform. Organizations run short online campaigns, participants share a personal store link from a mobile app, supporters buy a physical product through Shopify, and third-party manufacturing partners ship direct to the buyer. We have a complete written specification, a defined MVP scope, and a target of production-ready and live in both app stores by the end of January 2027. We are looking for one developer (or a small team) to build the MVP end to end. You will work from our spec in your own repository branch, deliver in milestones, and use AI-assisted development tools as your standard workflow. What you will build Native mobile app for campaign participants (iOS and Android, React Native with Expo preferred): onboarding, personal dashboard, leaderboard, push notifications, and a message toolkit that lets users pick contacts and send pre-written messages from their own device Web app for organizers (create and launch campaigns, track progress) and a master admin dashboard (campaign management, sales and order metrics, batch status, payout statements, settings) Public store pages with QR codes that hand off to Shopify checkout with campaign and participant attribution Shopify integration: custom app, order webhooks with signature verification and deduplication, nightly reconciliation, fulfillment write-back Automated order batching: on campaign close, generate production and fulfillment files, route to the correct manufacturing partner by configurable rules, deliver by API, SFTP, or email, and ingest tracking back into Shopify Payout calculation engine with PDF and CSV statements, built as one tested module Role-based access, audit logging, error monitoring, and backups Must have Shipped at least one production Shopify custom app using the Admin API and webhooks Shipped at least one app to both the App Store and Google Play Strong Next.js, TypeScript, PostgreSQL, and background job experience Experience with file-based integrations (CSV or SFTP) to external systems Daily use of AI coding tools (Claude Code, Cursor, or equivalent) with a track record of maintaining project rules files and tests Clear written communication in English and availability for a weekly demo call (US Central time) Nice to have Expo push notifications and native contact picker experience Shipping or address validation APIs (EasyPost, Shippo, or similar) Payout or ledger systems where correctness was audited Prior work with fundraising, marketplace, or multi-tenant products How we work Full written specification provided after a short NDA Seven milestones with acceptance criteria, paid per milestone Tests required on all money math, order attribution, and batching logic Weekly demo on a phone, not a laptop A senior reviewer approves pull requests before merge Engagement Fixed price per milestone Estimated start: 11-9-2026/ASAP Estimated duration: 8 to 10 weeks Post-launch support retainer available to the right developer To apply, please include A link to a Shopify custom app you built and a mobile app you shipped to both stores One paragraph on how you handle a Shopify webhook that arrives twice Your typical AI-assisted workflow in three sentences Your availability through February 2027