React Native Engineer

Engagement context

We partner with a US health‑tech company to take over a production AI-powered mobile coaching React Native app.

• React Native with Hermes, bridgeless mode
• TypeScript
• Zustand, TanStack Query 5
• NativeWind (Tailwind for RN)
• Skia, Reanimated 4
• Nitro Modules (JSI) including a Kotlin SDK bridge for fitness equipment
• Zod
• Auth0

App ships to iOS and Android with real users.

Role summary

Senior React Native Engineer — Mobile track lead. Pair with Senior Android/Kotlin engineer (native bridge), set codebase standards, lead audits and knowledge transfer, and ship features. Player‑coach: ~70% hands-on, ~30% leadership (architecture, code review, hiring).

What you'll do

First 90 days

• Document codebase with outgoing team
• Establish quality baseline: TS strictness, tests, deps, app size, cold start, frame‑rate
• Audit JSI / Nitro bridges, focus on Kotlin fitness SDK bridge
• Identify risky screens/flows and propose stabilization plans
• Lead knowledge‑transfer sessions

Ongoing

• Own mobile architecture
• Lead design reviews
• Pair with mid‑level engineers
• Manage app‑store pipelines
• Participate in on‑call for mobile crashes

Offer:

• Location: 100% remote
• Engagement: B2B
• Rate: up to PLN 175 p/h
• Start: July

Must-have skills

• 5+ years mobile development, of which 3+ years React Native in production
• React Native bridgeless mode + Hermes — production experience, not just exposure
• JSI / Nitro Modules — built or maintained at least one native module bridge in production. Nitro Modules specifically is rare — JSI native-module experience is acceptable; pure Nitro is a bonus.
• TypeScript strict mode — generics, narrowing, no any-as-escape
• State management with Zustand (or comparable: Redux Toolkit, Jotai)
• TanStack Query / React Query at production scale
• Reanimated 4 + gesture-handler — building actual animated UIs
• Auth0 mobile SDK or comparable OIDC mobile flow
• iOS native integration — Xcode comfort, Swift/Objective-C reading, CocoaPods, app provisioning, TestFlight
• Android native integration — Android Studio comfort, Gradle, Kotlin reading
• App-store deploy pipelines — Fastlane, Bitrise, or EAS Build
• Crash analytics — Firebase Crashlytics or comparable
• Working English

Nice-to-haves

• Skia / GPU rendering in RN
• NativeWind or Tailwind-for-RN
• Bluetooth Low Energy (BLE) integration in RN
• HealthKit / Health Connect integration
• Experience working with a multi-platform native SDK that's owned by another team