Frontend Developer

Mobile Engineer (React Native / Expo)

About Onyx

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 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 Do

• Build and scale the Onyx mobile application using React Native, Expo, and TypeScript

• Develop polished, intuitive, and highly performant experiences across iOS and Android

• Own mobile features from technical design through development, testing, release, and monitoring

• Manage production builds, submissions, releases, and over-the-air updates using Expo Application Services

• Personally own releases through both the Apple App Store and Google Play Store

• Handle certificates, provisioning profiles, app signing, versioning, review requirements, and release approvals

• Integrate the mobile application with backend APIs, AWS services, and real-time data infrastructure

• Build responsive experiences powered by live data, streaming updates, and WebSockets

• Identify and resolve issues related to performance, reliability, scalability, and production stability

• Create reusable components and help shape a scalable mobile architecture

• Partner closely with Product, Design, Backend Engineering, and Infrastructure

• Contribute to code reviews, testing standards, CI/CD workflows, and broader engineering practices

What We’re Looking For

• 2+ years of professional mobile engineering experience

• Strong production experience with React Native, Expo, and TypeScript

• Hands-on experience using EAS Build, EAS Submit, and Expo Updates

• Experience personally shipping and maintaining consumer applications through both the Apple App Store and Google Play Store

• Strong knowledge of the complete mobile release lifecycle, including signing, certificates, provisioning, versioning, store review, and release management

• Strong understanding of mobile architecture, state management, debugging, testing, and performance optimization

• Experience integrating mobile applications with REST APIs and cloud-based services

• Strong product judgment and attention to detail, particularly across high-quality consumer experiences

• Ability to independently own mobile features and production releases in a fast-moving startup environment

Nice to Have

• Experience with WebSockets, real-time data, animations, payments, fintech, trading, sports, gaming, or other highly interactive consumer applications

• Experience working with AWS-based infrastructure

• Native iOS experience with Swift and/or Android experience with Kotlin

Non-Negotiable Requirements

• Production experience with Expo

• Direct ownership of App Store and Google Play Store submissions and releases

• Existing authorization to work in the United States without current or future visa sponsorship

Onyx is unable to provide visa sponsorship for this role.