Cross-Platform Social Event App with Real-Time Discovery, QR Check-In & Intelligent Matching
How we built a React Native social networking app that connects people through local events — featuring GPS-based discovery, proximity-verified QR check-in, and a custom recommendation algorithm.
A social networking startup wanted to build a cross-platform mobile app that lets users discover, sign up for, and check in to real-time social events around them. The core challenge: QR-based check-in had to be proximity-verified (only scannable within the event's physical range), and event recommendations needed to balance time relevance, geographic distance, event type, and user preferences — all in a snappy, real-time feed.
Four problems we were handed to solve.
No existing solution combined event discovery with proximity check-in
Existing event platforms had no way to verify physical attendance. The client needed QR check-in that only works within GPS range of the event — preventing remote or fraudulent check-ins.
Event recommendations needed to balance multiple relevance factors
A simple distance sort wasn't enough. The algorithm had to weigh time (upcoming vs. later), distance (nearby vs. far), event category match, and user interaction history to produce a truly relevant feed.
Cross-platform native integrations required (GPS, Camera, Maps)
The app needed deep integration with device GPS for location tracking, camera for QR scanning, and native map rendering — all performing smoothly on both iOS and Android.
Real-time event feed with sub-200ms response time at scale
With thousands of concurrent users browsing nearby events, the backend had to serve geo-filtered, scored, and ranked event feeds in under 200ms per request.
The Strategy & Implementation Plan
React Native Cross-Platform Build
Built the app in React Native with Expo, enabling a single codebase for iOS and Android. Native modules integrated for GPS (continuous location), Camera (QR scanning), and MapView (interactive event map with clustering).
Weighted Recommendation Algorithm
Developed a custom event scoring engine using weighted sum: score = w₁(time_relevance) + w₂(distance_score) + w₃(category_match) + w₄(user_history_relevance). Weights tuned through A/B testing to maximise engagement.
Proximity-Verified QR Check-In
Each event generates a unique QR code. On scan, the app verifies the user's GPS coordinates are within the configured event radius (default 100m). Check-in only succeeds if location validation passes — preventing remote fraud.
FastAPI + PostgreSQL Backend
High-performance API built with FastAPI (Python) and PostgreSQL with PostGIS extension for geospatial queries. Real-time event feed served via spatial indexing. WebSocket support for live event updates and attendee counts.
Results & Upgraded System
The upgraded system delivered measurable transformation across all key metrics. What was once a manual, error-prone process is now fully automated with real-time visibility and intelligent exception handling.
Collaboration model & success factors.
Native-Quality UX from Shared Codebase
React Native with carefully chosen native modules delivered 60fps map rendering, instant camera access, and smooth GPS tracking — matching the experience of fully native apps while shipping 2× faster.
Algorithm Tuned Through Real User Behavior
We launched the recommendation engine with baseline weights, then A/B tested weight configurations over 4 weeks. Final weights were derived from actual engagement data, not assumptions.
Geospatial Engineering Expertise
PostGIS spatial indexing, GPS accuracy handling (including indoor/outdoor fallback logic), and proximity circle calculations were handled by engineers with prior geolocation app experience.
More stories from the field.
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