Senior Full-Stack Product Engineer : Next.js / TypeScript / Supabase / Stripe . AI-Native.

We are looking for a senior full-stack product engineer to take technical ownership of an existing SaaS product. This is not a design role and not a junior/mid-level development position. We need someone who can understand an existing codebase, make sound architectural decisions, ship production features independently, and take responsibility for whether what they build actually works. Our stack includes: Next.js TypeScript PostgreSQL / Supabase Stripe Authentication / user permissions API integrations Modern cloud deployment AI-assisted development tools You should be comfortable owning a feature end-to-end: database → backend → frontend → authentication/permissions → payments → testing → deployment → monitoring/fixes. What you'll work on Your initial responsibility will be an existing SaaS platform. Current and upcoming work includes: User and company dashboards Credits/billing systems Stripe payments Authentication and permissions Guest/user flows QR-based interactions Database and API work Security and access controls Bug fixing and production reliability Improving existing architecture where necessary Shipping new features from clear product requirements Later, if the collaboration works well, you may take technical ownership of additional products. How we work We already work successfully with a senior engineer who uses modern AI coding tools extensively to increase development speed and quality. We expect the same mindset. We are not interested in someone who manually spends three days on work that modern tooling can help a strong engineer complete in hours. At the same time, AI-generated code must be understood, reviewed, tested and production-ready. We care about engineering judgment, security and maintainability not simply generating code quickly. You will work from a prioritized ticket queue: Understand → build → test → ship → demonstrate that it works. We value proof over promises. Requirements You should have strong, demonstrable production experience with: Next.js TypeScript PostgreSQL and/or Supabase Stripe integrations Authentication and authorization SaaS architecture API development/integrations Git/GitHub Production deployment Application security AI coding tools such as Claude Code, Cursor, Codex or equivalent You should be capable of entering an existing codebase and becoming productive quickly without requiring constant technical supervision. Engagement Starting commitment: 20 hours/week If the collaboration is successful, we expect to increase this to approximately 40 hours/week. This is intended to become a long-term relationship rather than a short freelance assignment. An NDA and IP assignment agreement must be signed before access to any source code or confidential technical information is provided. Important: how to apply Please do not send us a generic AI-generated proposal. Start your application with the words: “I ship products.” Then provide: Links to 2–3 production SaaS products you personally worked on. Explain exactly what you built on each. One example of a production Stripe integration you implemented. One example involving authentication/permissions/security. Your experience with Next.js + TypeScript + Postgres/Supabase. Which AI coding tools you use daily and specifically how they change your development workflow. Your GitHub profile, if available. Your hourly rate and availability for the next 3 months. If you cannot show real production work, please don't apply. Screening question: You inherit an existing Next.js/TypeScript/Supabase SaaS application with Stripe billing. Before shipping your first feature, what do you inspect during your first 48 hours? Be specific.