Mobile App MVP: Cross-Platform Fitness Tracker in 2 Weeks
A React Native fitness tracking app with workout logging, progress photos, and social challenges, shipped to both app stores in 14 days.
Client: FitCircle (Pre-seed startup)
Mobile app screenshots showing workout logging screen with exercise picker, progress photo grid with before/after comparison, and social feed with friend activity and challenge cards.
The Challenge
The fitness app market is saturated with complex apps like MyFitnessPal and Strong, but the founder identified a gap: none of them had meaningful social features. His target audience was gym partners who wanted to stay accountable to each other. He had a Figma prototype and 500 people on a waitlist from an Instagram campaign. The challenge was shipping a real app to both iOS and Android before the waitlist went cold. He had tried Flutter but his dev partner dropped out mid-project, leaving half-finished code that nobody else could maintain. He needed a team that could ship fast on both platforms without platform-specific headaches.
Our Approach
React Native with Expo was the obvious choice for cross-platform speed. We used Expo Router for file-based navigation (mirroring Next.js patterns the team already knew) and NativeWind for Tailwind-style styling. The backend was Hono on Railway with PostgreSQL and Drizzle ORM, keeping the same stack as our web projects for consistency. Day 1 through 3 built the auth flow (Apple Sign-In + Google) and core navigation structure. Days 4 through 7 focused on the workout logger: exercise search (from a seeded database of 500+ exercises), set/rep tracking, and rest timer. Days 8 through 10 were the social layer: friend system, activity feed, and weekly challenges with leaderboards. Days 11 through 12 handled progress photos with a swipe comparison view. Day 13 was App Store and Play Store submission prep (screenshots, descriptions, privacy policy). Day 14 was the submission itself plus backend deployment.
What We Built
Delivery Timeline
Day 1-3: Foundation
Auth flow (Apple + Google), Expo Router navigation, Hono backend scaffold, database schema.
Day 4-7: Workout Logger
Exercise database, set/rep tracking UI, rest timer, workout history view.
Day 8-10: Social Layer
Friend system, activity feed, weekly challenge creation, leaderboard rankings.
Day 11-12: Progress Photos
Camera integration, S3 upload, before/after swipe comparison view.
Day 13: Store Prep
App Store and Play Store assets, screenshots, privacy policy, submission.
Day 14: Launch
Backend production deployment, push notification setup, founder walkthrough.
Tech Stack
Architecture
frontend
React Native with Expo, Expo Router, and NativeWind.
backend
Hono on Railway with Drizzle ORM on PostgreSQL.
auth
Apple Sign-In + Google Sign-In via Expo Auth.
data
PostgreSQL for relational data. S3-compatible storage for photos.
notifications
Expo Push Notifications with server-side scheduling.
Security
rbac
User-level data isolation. Friends-only visibility for progress photos.
secrets
Railway environment variables. App signing keys in GitHub Secrets.
monitoring
Sentry React Native SDK for crash reporting.
qa
Detox E2E tests for critical flows (auth, workout logging, photo upload).
The Results
“My last dev ghosted me with half-built Flutter code. HouseofMVPs shipped a polished app to both stores in 2 weeks. My waitlist converted at 68% on day one.”
Key Takeaways
React Native with Expo eliminates 80% of platform-specific pain. EAS Build handles signing, and Expo Router gives you file-based routing identical to Next.js.
Seed the exercise database before launch. We pre-loaded 500+ exercises with muscle group tags so the app felt complete from the first open.
App Store review takes 24-48 hours. Submit on Day 13, not Day 14. We almost missed the deadline waiting for Apple review.
Deliverables
FAQ
Frequently Asked Questions
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