Mobile Product Experience Engineer

What you’ll own

The mobile experience that makes Calibrex feel indispensable in the gym: Expo/React Native screens, core workout flows, onboarding, interaction patterns, the design system, and the user-facing details that make coaching feel fast, clear, and trustworthy. You will own the experience of starting, executing, and reviewing a workout, not just implementing screens handed to you.

You’ll work closely with the founder, who owns the overall architecture and system boundaries, and with our Product Systems & Integrations Engineer, who owns the underlying data, services, and integrations. Your job is to turn product feedback into fast, polished iterations and to use Codex as a serious force multiplier, not a substitute for engineering judgment.

This is a high-agency role. One week you may be making the training flow feel effortless under load; the next you may be tightening onboarding, designing a better device-connection state, improving progress/history, or making an error state understandable in half a second.

You should have

Strong production experience with React Native and Expo
Shipped consumer-facing mobile features end to end, from product detail to App Store / Play Store release
Excellent TypeScript and React fundamentals
Exceptional product and UI/UX instincts: you care about information hierarchy, responsive interaction, clear states, and the details that make an app feel trustworthy
Experience building or contributing to a coherent mobile design system and translating product intent into durable, reusable UI
Comfort integrating Firebase-backed features and collaborating across data, API, and native boundaries
A practical, disciplined workflow with Codex or comparable AI-assisted development tools; you can move quickly while reviewing, testing, and owning what ships

Nice to have

Experience designing or implementing real-time, audio, BLE, wearable, sensor, or background-runtime experiences
Expo dev-client or native iOS/Android debugging experience
Experience with subscriptions, payments, HealthKit, or mobile analytics and experimentation
Startup experience on a small team
Experience with agentic loops, subagents, and second-brain systems

Who you are

Fitness-first and accountable. You lift weights regularly and take training seriously—this is not a perk box to check. You need to understand the product on your body, recognize when a cue or workout flow feels wrong, and care about the athletes we build for.