Senior Software Engineer – Fullstack

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 ethers.js, viem, or similar client libraries for interacting with smart contracts
• Deep knowledge of JavaScript/TypeScript language features, idioms, and best practices, with the ability to influence team standards
• Strong understanding of performance optimization, responsive design, accessibility, and web standards
• Experience integrating with backend APIs and collaborating with cross-functional platform/infra teams
• Experience with CI/CD pipelines, testing strategies, and safe deployment practices for web applications
• Team-first mentality, with a willingness to do what it takes to get the job done and a desire to strive for better
• Demonstrated experience using AI tools (Claude Code, Codex, Cursor, Copilot, etc.) to ship production code
• Can demonstrate specific examples of workflow improvements (e.g., “reduced boilerplate generation time by 40%”)
• Effectively communicates complex technical concepts clearly to diverse audiences, including engineers and stakeholders
• Thrives in a high-growth environment where priorities evolve regularly and decisions are made quickly
• Strong ability to collaborate cross-functionally across diverse teams within large enterprise environments, supporting alignment and shared success

Preferred Qualifications:

• Previous experience in 0→1 or high-growth startup environments
• Contributions to open-source projects or technical community
• Experience with real-money transaction systems and regulatory compliance
• Background in building developer tools or improving engineering productivity
• Experience leading without authority and influencing technical direction across teams