Backend Tech Lead: Multi-Tenant Payments Platform (Node.js/NestJS, Authorize.net), Fixed Price

We're building a modern platform around a legacy Windows point-of-sale system (VB6 on SQL Server): a cloud backend, customer apps, a merchant portal, a platform admin portal and integrations with Authorize.net and in-store card terminals. Separate developers own the VB6/SQL Server connector, the card terminals, the payments backend, the apps and QA. You will lead the backend and the technical direction. What you'll own: - Platform architecture: Node.js/NestJS (or .NET), multi-tenant SaaS, role-based access and audit logs - Durable messaging (Kafka or RabbitMQ) between the cloud and the store connector, with safe retries - API design for the apps and portals, code reviews, test strategy and documentation - Technical guidance for the payments engineer so every payment posts exactly once and unknown results recover safely Budget: fixed price of USD 20,000 for the role, paid in milestones as each phase is accepted, with the final milestone paid after the in-store pilot is signed off. Timeline: about 30 hours per week over roughly 8 to 9 months, starting late November. To apply, tell us: 1. One or two production systems you built that are closest to this, and what your role was 2. Confirm you can take the role at the fixed USD 20,000, paid by milestone 3. How many hours per week you can commit from late November Proposals without specific production experience will not be considered.