Senior Mobile Engineer

Topstep

12d•$157,000 - $193,000•Hybrid

About The Position

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 Senior Mobile Engineer 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 mentor engineers who are building the next generation of our mobile platform. Join us and help define what mobile excellence looks like at Topstep.

Requirements

5+ 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.
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.
Track record of technical leadership through architectural documentation, code reviews, component libraries, and establishing mobile engineering standards.
Excellent communication skills with the ability to explain mobile-specific constraints and trade-offs to varied audiences and build consensus across teams.
Comfortable making pragmatic decisions, balancing long-term mobile architecture with immediate feature delivery and MVP launch goals.
Ability to add, subtract, multiply, and divide in all units of measure, using whole numbers, common fractions, and decimals. Ability to compute rate, ratio, and percent, and to draw and interpret bar graphs.
Ability to apply concepts such as fractions, percentages, ratios, and proportions to practical situations.
Ability to apply common sense understanding to carry out written or oral instructions. Ability to deal with problems involving concrete variables in standardized situations. Ability to solve practical problems via a logical, analytic approach.
Knowledge of electronic equipment, intermediate PC skills, knowledge of internet software and proficiency. Familiarity with Google Drive and Google Docs is a must. Computer experience/operation is required. Must have the ability to operate general office equipment.
Ability to multitask.
Ability to work in a fast-paced environment.
Strong time management and organizational skills.
Ability to work under dynamic schedule constraints and consistently meet deliverable timelines.

Nice To Haves

Experience building financial, trading, or fintech mobile applications where real-time data, reliability, and security are critical.
Background with native iOS (Swift/Objective-C) or Android (Kotlin/Java) development, and understanding when to drop down to native code.
Experience with real-time data integration using WebSockets or Server-Sent Events.
Familiarity with mobile authentication patterns (biometrics, OAuth, secure token storage).
Experience with complex mobile UI patterns (charts, animations, gesture handling).
Background building and maintaining shared component libraries or design systems for mobile.
Experience with Expo or similar React Native development platforms.
Understanding of mobile security best practices and secure coding for sensitive financial data.

Responsibilities

Lead 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.
Own 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.
Drive 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.
Mentor engineers on 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.