Senior React Native Expo Engineer

## About the Role At Mochi, our engineering team operates with exceptional leverage. We believe in high talent density, where a focused, elite team powers a profitable, nine-figure ARR healthcare platform serving hundreds of thousands of patients. We are looking for a Senior React Native Engineer to own the mobile applications that serve as the primary daily touchpoint for our patients and providers. Mochi has already helped patients lose over 5 million pounds through metabolic care, and we are now rapidly expanding into the frontiers of preventative healthcare—including hormone optimization (HRT/TRT), longevity medicine, and cutting-edge peptide therapies. The mobile experiences you architect will directly dictate how this next wave of patients tracks sensitive biometrics, communicates securely with their care teams, and manages complex medication protocols. Because of our high scale-to-team ratio, we do not operate in isolated technical silos. You will act as our mobile product specialist, owning the application end-to-end: from architecting offline-first data synchronization and deep native health integrations, to leveraging Expo to deliver a modern, unified cross-platform experience. If you are drawn to mobile product problems where the domain complexity is real, the autonomy is absolute, and the impact on patient outcomes is tangible, this is the role. ## What You'll Do - Architect the Mobile Clinical Experience: You will build the dynamic, high-performance mobile tools our patients and providers rely on. You will architect deep integrations with Apple HealthKit and Google Health Connect to seamlessly ingest and visualize real-time patient data, and build highly responsive, secure messaging systems that connect patients directly to their care teams without friction. - Leverage the Expo Ecosystem: You will treat our mobile infrastructure as a product advantage. You will leverage the full power of Expo to deliver a flawless, cross-platform experience, utilizing EAS (Expo Application Services) to manage our build pipelines, configure custom native modules via Config Plugins, and push seamless over-the-air (OTA) updates to iterate rapidly and ensure patients always have the latest clinical tools. - Design for the Edge: Mobile healthcare apps must work in the real world—which means handling spotty cellular connections and offline states gracefully. You will architect robust, offline-first data synchronization strategies and implement aggressive local caching to ensure patients can always access their care plans. - Champion the Mobile UX: You are a mobile product specialist. You don't just implement designs; you obsess over the details that make an app feel premium and native. You sweat the frame rates, the navigation stack transitions, the keyboard avoidance behaviors, and the accessibility standards required to support a diverse patient population. - Build Agentic Workflows: Mochi is an AI-first engineering org. You will not only utilize frontier agentic models to accelerate your own development, but you will also integrate AI capabilities directly into our mobile interfaces to automate clinical operations and streamline patient support. - Raise the Engineering Bar: Own key mobile architectural decisions, establish patterns for strict code reuse between our web and mobile clients, and elevate the engineers around you through rigorous code review and mobile testing practices. ## Who You Are - You have operated high-stakes mobile systems. You have 5-7+ years of frontend engineering experience, with deep, specialized focus on React Native and Expo. You've built, shipped, and maintained complex, data-heavy mobile applications in production. - You are an Expo and Mobile Infrastructure expert. You understand the modern Expo ecosystem deeply. You know how to manage EAS builds, integrate complex native modules (like HealthKit/Health Connect) without ejecting, and navigate the strict review guidelines of the iOS App Store and Google Play Store. - You master mobile state and performance. You understand the React render cycle on mobile. You know how to prevent UI thread blocking, optimize list rendering for massive messaging datasets, and orchestrate complex asynchronous data fetching securely. - You are a full lifecycle owner. You build things that run in production, not just pass review. You view managing the CI/CD pipeline, monitoring crash rates (e.g., Sentry for mobile), and owning your app's reliability in the wild as a fundamental part of your job. - Your workflows are altered by AI. You are already using frontier agentic tools (e.g., Codex 5.3, Claude Opus 4.6) to build faster. You can describe specific ways these models have structurally changed how you code, while retaining the deep technical skepticism required to audit, verify, and own its output. - You are a collaborative builder. You have low ego, high standards, and excellent communication skills. You thrive in cross-functional environments where engineering requirements are heavily shaped by healthcare regulations, compliance, and patient safety. - You are excited to work in-person. You want to build alongside the team 5 days a week in our San Francisco office. - If you are targeting Staff leveling: We expect a demonstrated track record of setting technical direction across teams, navigating deep ambiguity, and measurably leveling up the engineers around you. - Our mobile stack is React Native, Expo, TypeScript, and modern state management tools. Experience with native iOS (Swift/Objective-C) or Android (Kotlin/Java) is a strong plus for when we need to drop down into native code, but we index on React Native mastery and product sense. ## Our Process We respect your time. Here is exactly what to expect: - Intro call (30 min, remote) — Chat with our recruiter about the role and expectations. - Technical round (2