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Healthcare · Fitness8 monthsSenior React Native Developer
Running Coach
Fitness & Performance Tracking
Performance-optimized fitness app with GPS tracking, workout analytics, and offline-first architecture for athletes who train without reliable connectivity.
60%
Load time reduction
30%
Battery improvement
10K+
Active athletes
4.8★
App Store rating
React NativeExpoMapsGPSOffline Sync
Product Preview
The Challenge
GPS tracking that works when athletes need it most
- —Runners and coaches needed accurate route tracking, pace analytics, and workout history — even in areas with poor connectivity.
- —Battery drain from continuous GPS usage was a top user complaint in competing apps.
- —The product had to feel native-smooth during long outdoor sessions.
Product Goals
- ✓Deliver reliable GPS tracking with minimal battery impact
- ✓Build offline-capable data layer for workout sync
- ✓Achieve 60fps UI during active tracking sessions
The Solution
Offline-first architecture with optimized location services
- —Implemented background location tracking with intelligent batching to reduce battery drain
- —Built offline queue for workout data with automatic sync when connectivity returns
- —Designed map visualizations and analytics dashboards with Reanimated for smooth interactions
Architecture
- ✓Expo with custom native modules for location
- ✓MMKV for fast local persistence
- ✓Background task scheduling for sync
- ✓Mapbox integration with route polyline rendering
Technical Highlights
How It Was Built
GPS & background location
Offline-first data sync
Maps & route visualization
Battery optimization
Reanimated animations
Health data integration
Lessons Learned
- →Location-heavy apps need performance budgets defined before feature development
- →Offline sync architecture should be designed on day one, not bolted on later
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