Frontend Developer

Mobile Engineer (React Native / Expo)About OnyxOnyx 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 expanding the engineering team behind our real-time consumer platform. We’re looking for a product-minded Mobile Engineer with deep, hands-on experience building and shipping production applications with React Native, Expo, and TypeScript.This role will own meaningful parts of the Onyx mobile experience across iOS and Android—from architecture and feature development through App Store submission, release, and ongoing performance. You should be comfortable moving quickly, working across the stack when needed, and taking complete ownership of what reaches users.What You’ll DoBuild and scale the Onyx mobile application using React Native, Expo, and TypeScriptDevelop polished, intuitive, and highly performant experiences across iOS and AndroidOwn mobile features from technical design through development, testing, release, and monitoringManage production builds, submissions, releases, and over-the-air updates using Expo Application ServicesPersonally own releases through both the Apple App Store and Google Play StoreHandle certificates, provisioning profiles, app signing, versioning, review requirements, and release approvalsIntegrate the mobile application with backend APIs, AWS services, and real-time data infrastructureBuild responsive experiences powered by live data, streaming updates, and WebSocketsIdentify and resolve issues related to performance, reliability, scalability, and production stabilityCreate reusable components and help shape a scalable mobile architecturePartner closely with Product, Design, Backend Engineering, and InfrastructureContribute to code reviews, testing standards, CI/CD workflows, and broader engineering practicesWhat We’re Looking For2+ years of professional mobile engineering experienceStrong production experience with React Native, Expo, and TypeScriptHands-on experience using EAS Build, EAS Submit, and Expo UpdatesExperience personally shipping and maintaining consumer applications through both the Apple App Store and Google Play StoreStrong knowledge of the complete mobile release lifecycle, including signing, certificates, provisioning, versioning, store review, and release managementStrong understanding of mobile architecture, state management, debugging, testing, and performance optimizationExperience integrating mobile applications with REST APIs and cloud-based servicesStrong product judgment and attention to detail, particularly across high-quality consumer experiencesAbility to independently own mobile features and production releases in a fast-moving startup environmentNice to HaveExperience with WebSockets, real-time data, animations, payments, fintech, trading, sports, gaming, or other highly interactive consumer applicationsExperience working with AWS-based infrastructureNative iOS experience with Swift and/or Android experience with KotlinNon-Negotiable RequirementsProduction experience with ExpoDirect ownership of App Store and Google Play Store submissions and releasesExisting authorization to work in the United States without current or future visa sponsorshipOnyx is unable to provide visa sponsorship for this role.