Mobile Engineer (React Native / Expo)

Mobile Engineer (React Native / Expo) Onyx is building the consumer trading platform for the speculation economy—bringing prediction markets, sports, crypto, and real-world events into one seamless experience. Following our Series A led by Payward, we're growing the engineering team behind our real-time, consumer-first trading platform. We're looking for a Mobile Engineer with strong production experience in React Native, Expo, and TypeScript to build and scale the Onyx mobile experience across iOS and Android. This is a high-impact opportunity to own mobile features from concept through release and help shape the future of our mobile platform. What You'll Do Build and scale high-quality mobile applications using React Native, Expo, and TypeScript Develop polished, performant user experiences across iOS and Android Own features from technical design through development, testing, deployment, and monitoring Manage builds, releases, and over-the-air updates using Expo Application Services (EAS) Own submissions and releases through the Apple App Store and Google Play Store Navigate app review requirements, certificates, provisioning profiles, signing, versioning, and release approvals Integrate the mobile application with backend APIs and AWS-based services Build real-time experiences powered by live data and streaming updates Optimize application performance, responsiveness, reliability, and scalability Create reusable components and contribute to scalable mobile architecture Partner with Product, Design, Backend Engineering, and Infrastructure to deliver new features Debug production issues and improve the customer experience Contribute to code reviews, testing, CI/CD workflows, and engineering best practices What We're Looking For 2+ years of professional mobile engineering experience Strong production experience with React Native, Expo, and TypeScript Expo experience is required and non-negotiable Hands-on experience shipping and maintaining consumer applications through both the Apple App Store and Google Play Store Strong knowledge of the end-to-end submission and release process, including app signing, provisioning, certificates, review requirements, versioning, and release management Experience with EAS Build, EAS Submit, and Expo Updates Strong understanding of mobile architecture, state management, testing, debugging, and performance optimization Experience integrating mobile applications with REST APIs and cloud-based services; AWS experience is preferred Strong product intuition and attention to detail, with a focus on polished consumer experiences Comfortable owning mobile features and releases end-to-end in a fast-moving startup environment Experience with animations, WebSockets, real-time data, payments, sports, gaming, fintech, trading, or other interactive consumer products is a plus Native iOS experience with Swift and/or Android experience with Kotlin is a plus Logistics Location: NoHo, New York City Schedule: Hybrid Experience: 2+ years Work Authorization: Candidates must already be authorized to work in the United States. Onyx cannot provide current or future visa sponsorship for this role.