Summary Are you a mobile engineer who thrives on building exceptional user experiences, shipping high-quality apps from scratch, and raising the technical bar for teams around you? As a Mobile Engineer III at Topstep, you'll play a foundational role in building our mobile trading platform using React Native. You'll be instrumental in launching our MVP, establishing mobile architecture patterns, and then embedding within feature teams to drive ongoing mobile development.

This is an opportunity to shape the mobile experience for traders and set the technical foundation that will scale across both our trader experience and trading experience platforms. This role is ideal for someone who brings both deep React Native expertise and a product mindset. Someone who's excited to own the mobile app end-to-end, establish reusable patterns and components that scale across teams, and work with a team who is building the next generation of our mobile platform.

Join us and help define what mobile excellence looks like at Topstep.

Key Responsibilities

Contribute to the mobile MVP effort to establish our React Native application from the ground up, integrating with GraphQL APIs across our trader experience and trading experience platforms. Establish engineering patterns for React Native development, including reusable components, custom hooks, TypeScript patterns, and testing strategies that other engineers can adopt. Contribute to end-to-end mobile features from design through App Store and Play Store releases, ensuring seamless integration with backend services and optimal performance.

Partner with product and design to translate trader needs into mobile experiences that balance user experience with technical constraints and platform capabilities. Contribute to mobile quality and performance by embedding testing, monitoring, crash reporting, and performance optimization into every feature you ship. Embed within feature teams after MVP launch to drive ongoing mobile development, bringing mobile expertise to cross-functional squads.

Uphold React Native best practices, mobile-specific architectural thinking, and production ownership. Champion mobile-first thinking across the organization, helping backend and frontend teams understand mobile constraints and opportunities.

Required Qualifications

and Key Competencies 3 + years of professional experience building production mobile applications, with demonstrated impact in establishing patterns and practices that scaled across multiple teams. Deep React Native expertise, including navigation (React Navigation), state management (Redux, Zustand, Context), native module integration, and performance optimization. Strong TypeScript and modern JavaScript foundation with understanding of React patterns, hooks, component composition, and functional programming concepts.

Cross-platform mobile development experience shipping apps to both iOS App Store and Google Play Store, including an understanding of platform-specific differences and capabilities. GraphQL client integration experience using Apollo Client or similar libraries, including cache management, optimistic updates, and error handling. Strong database fundamentals, including experience with PostgreSQL or SQL Server-schema design, migrations, indexing, and query optimization.

Mobile-specific performance optimization, including understanding of bundle size, startup time, memory management, list virtualization, and image optimization. Production mobile app experience, including crash reporting (Sentry, Crashlytics), analytics integration, remote config, and debugging production issues. Testing mindset with experience writing unit tests (Jest), integration tests, and E2E tests (Detox, Appium) for React Native applications.

Understanding of mobile CI/CD, including automated builds, code signing, TestFlight/Play Store distribution, and release management.