Senior Software Engineer - Fullstack

About 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 Senior Software Engineer role is an IC with significant ownership across our full stack: the web application customers use to interact with our product, and the backend systems that power it. Whichever side you're strongest on, you'll have real room to deepen your reach into the other as you join a product at an exciting early stage, helping define the product, technical foundations, and ways of working from scratch. 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, 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 experiences — whether that's front-end work in React, Next.js, and modern TypeScript, or backend work in Go (modeling data for markets, orders, and transactions) — while making meaningful contributions on the other side of the stack too
• Drive the technical evolution of our Markets 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
• 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 an early stage product environment, unblocking others and taking initiative where processes are still being defined

Qualifications:

• Over 6 years experience and/or operating at Senior/Staff level building highly scalable, production systems — whether that's user-facing web applications in modern JavaScript/TypeScript and React, or backend services in a language like Go, Java or Python. If you're frontend-strong, you don't need to arrive fluent in Go — just curious about what's happening beneath the UI
• Experience in React architecture, component-driven development, and modern state management patterns, libraries like NextJS, TanStack Query, Tailwind, Zustand — or, on the backend, experience with data modeling and event-driven architecture (e.g. Postgres, Kafka/PubSub)
• Deep knowledge of your primary language's features, idioms, and best practices (JavaScript/TypeScript or a backend language), with the ability to influence team standards
• Strong understanding of performance and reliability — responsive design, accessibility, and web standards on the front end; scalability, observability, and correctness on the backend
• 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

You don't need to tick every box — strength in one area and a willingness to learn goes a long way.

Preferred Qualifications:

• Previous experience in early-stage 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
• BSc in Computer Science or related field

Depending on the role, your interview and onboarding experience may include in-person components, such as onsite interviews or Launching into Better: LIVE—a multi-day cultural immersion in New York City for full-time, non-seasonal hires. These sessions are designed to build connections and bring our culture to life, though specific travel and participation requirements will be confirmed based on your role and location. Your recruiter will provide clear guidance at each stage of the process.

Ready to build the future of sports trading? If you possess some of these skills but not all of them, we still encourage you to apply! Please note that visa sponsorship is not available for this position. We are open to fully remote candidates based in the United Kingdom. Remote employees may also be eligible for a home office setup stipend.