Senior Full-Stack Engineer | Next.js, TypeScript, Supabase | Long-Term Contract

We’re looking for an experienced, hands-on full-stack engineer to help bring our existing applications to launch and take ownership of their continued development. Our work connects sports club management with team-apparel commerce and business operations. You’ll work directly with the founder to improve existing software, deliver new features, solve technical problems, and help shape practical engineering decisions. The applications are already substantially developed. The initial focus will be understanding the existing codebases, identifying launch priorities, completing important workflows, and establishing a dependable delivery process. What you’ll work on Our product roadmap spans two connected areas: • Sports club management: Registration, player and family accounts, teams and rosters, scheduling, coach and parent communication, notifications, payments, mobile experiences, and administrative dashboards. • Commerce and apparel operations: Product catalogs, team storefronts, apparel customization, inventory, purchasing, order management, production and fulfillment workflows, reporting, and external integrations. The broader roadmap also includes mobile experiences, design and customization tools, and practical AI features. We will prioritize this work in stages, with clear deliverables and realistic scope. Your responsibilities • Build complete features across the user interface, application logic, APIs, and database. • Improve responsive layouts, usability, accessibility, and performance. • Understand and extend existing code while preserving working functionality. • Develop reliable integrations between commerce, operational, and third-party systems. • Implement appropriate authentication, permissions, and separation of customer and organization data. • Diagnose defects, identify root causes, and add meaningful regression tests. • Maintain code review, automated checks, deployment practices, monitoring, and technical documentation. • Explain trade-offs clearly, raise concerns early, and recommend practical solutions. • Take responsibility for the quality and maintainability of the code you deliver. Core technology stack • Next.js, React, and TypeScript • Supabase and PostgreSQL • Stripe and Stripe Connect • GitHub and Vercel Experience with React Native/Expo, commerce or order-management systems, and interactive customization tools would be valuable. AI-assisted development We actively use AI coding tools and expect thoughtful, accountable use of them. You should be comfortable working with project instructions, coding agents, multiple review stages, automated tests, and security checks. You must be able to understand, debug, and maintain the resulting implementation yourself, including when an AI tool produces an incorrect solution. We measure progress through working features, reliability, and clear delivery and not just the volume of generated code. What we’re looking for • Demonstrated experience owning production applications across frontend and backend development. • Strong practical experience with our core stack. • Experience inheriting and improving an existing codebase. • Good product judgment and attention to the customer experience. • A disciplined approach to testing, security, and production releases. • Clear written and verbal communication and the ability to work independently. • An established Upwork track record with 100% Job Success and Expert-Vetted status. Please include in your proposal • One or two relevant applications you personally helped build or maintain, explaining your specific responsibilities. • Your experience with Next.js, TypeScript, Supabase/PostgreSQL, and commerce or operational workflows. • Your approach to AI-assisted development, testing, and code review. • Your hourly rate, available weekly hours, earliest start date, and overlap with U.S. Eastern Time. We’re looking for a dependable engineering partner who enjoys understanding a business, solving practical problems, and improving products over time.