Senior Software Engineer - Fullstack

About Us Fanatics is building a leading global digital sports platform. We ignite the passions of global sports fans and maximize the presence and reach for our hundreds of sports partners globally by offering products and services across Fanatics Commerce, Fanatics Collectibles, and Fanatics Betting & Gaming, allowing sports fans to Buy, Collect, and Bet. Through the Fanatics platform, sports fans can buy licensed fan gear, jerseys, lifestyle and streetwear products, headwear, and hardgoods; collect physical and digital trading cards, sports memorabilia, and other digital assets; and bet as the company builds its Sportsbook and iGaming platform. Fanatics has an established database of over 100 million global sports fans; a global partner network with approximately 900 sports properties, including major national and international professional sports leagues, players associations, teams, colleges, college conferences and retail partners, 2,500 athletes and celebrities, and 200 exclusive athletes; and over 2,000 retail locations, including its Lids retail stores. Our more than 22,000 employees are committed to relentlessly enhancing the fan experience and delighting sports fans globally. Fanatics Markets: Fanatics Markets is the real-money prediction and trading app where you can invest in moments you care about. Built on a secure platform, we let users predict real-world outcomes and trade on events they actually follow - from sports and entertainment to political elections and beyond. Our mission is to redefine how fans engage with the moments and markets that matter most. We're looking for the right people to help us build the future of prediction markets. Overview: This Software Engineer III (Full Stack) role is a senior-level IC with significant ownership over the web application that customers use to interact with our product. You'll join a product at an exciting early stage, helping shape its evolution as we continue to build core features, scale the platform, and refine the technical foundations. You'll lead by example, establishing best practices for AI-assisted development while building systems that can handle millions of events daily. On the engineering side, we're pioneering the use of AI as a code collaborator. We need engineers who have gone beyond experimentation—who actively use Claude Code, Cursor, Codex, GitHub Copilot, or similar tools to ship production code faster while maintaining exceptional quality standards. Responsibilities: Lead the design, development, testing, and deployment of scalable, high-quality web experiences using React, Next.js, and modern JavaScript/TypeScript Drive the technical evolution of our Markets web platform, partnering closely with product and design to deliver engaging, performant, and accessible features Own features end-to-end: spec writing → implementation → instrumentation → deployment → monitoring → iteration based on metrics Design and implement experimentation capabilities (feature flags, A/B tests) to validate ideas quickly and safely Integrate with backend APIs and collaborate with platform teams to build reliable, observable systems Make contributions to the Go backend Conduct thorough code reviews, raising the bar on code quality, readability, and maintainability Leverage AI tools to accelerate development velocity while maintaining high standards for security, correctness, and performance Establish and document team standards for AI usage (prompt patterns, code review checklists, validation strategies) Contribute to a fast-paced 0→1 environment, unblocking others and taking initiative where processes are still being defined Qualifications: Over 4 years experience building highly scalable, user-facing web applications using modern JavaScript/TypeScript and React Experience in React architecture, component-driven development, and modern state management patterns, libraries like NextJS, TanStack Query, Tailwind, Zustand Familiarity with common web3 libraries such as et…