Case studies organized by what I built at each company.
See the résumé for the full chronology.
Led React Native client delivery for a rewards app on a two-person team, establishing the project's testing, technical-documentation, and CI automation foundations from nothing across 144 pull requests in 82 days — treating the docs a future engineer reads and the gates their code must pass as the deliverable.
Platform Modernization and Native Modules
- Led the React Native New Architecture (TurboModule/Fabric) migration and the RN 0.81 + Node 22 LTS upgrade, and designed a deploy-tracking tag convention while running 15+ store releases and 19+ OTA deployments.
- Designed and built three native libraries — on-device receipt OCR (ML Kit, VisionKit + Vision), a reward-ad SDK, and an offerwall SDK — moving receipt-recognition preprocessing from the server to the client. Also implemented Naver OAuth 2.0 login and a module wrapping Google Play In-App Review and Apple StoreKit `requestReview` behind a single API, in Swift/Objective-C and Kotlin.
Data Layer and Quality Operations
- Unified four analytics SDKs (Amplitude, AirBridge, Notifly, Firebase) behind a single `Analytics.track()` interface, migrated 30+ files off direct SDK calls, and pinned the event taxonomy to a codegen contract that gates schema drift.
- Owned and filed 220 Jira issues, 139 of which shipped, and resolved 14 user-reported incidents. Diagnosed three separate root causes behind unpaid ad rewards and then designed a server-to-server callback structure, and — at 96.62% crash-free users — introduced a crash-ticketing process and an error-reporting abstraction.
Led the 0-to-1 launch, operational stabilization, and continuous improvement of a Flutter (iOS/Android) app for a pet behavior/personality-type assessment and expert consultation platform.
Payment Policy and PortOne
- Resolved payment/policy issues (Apple review/payment policy) and built three PG payment integrations on PortOne, laying the groundwork for launch and B2B/B2G expansion.
- Worked directly with Apple Developer Relations to clarify the service model (domestic-only, offline brokerage) and resolve App Review and payment-policy issues.
- Standardized the payment flow on PortOne and developed and published the `portone_flutter_v2` package.
- Led contracting and integration for three payment gateways (Toss Payments, Toss Pay, Kakao Pay).
Product Architecture and UI/UX
- Structurally managed state, model, and routing complexity using Riverpod, Freezed, and go_router.
- Achieved 85%+ positive responses for UI/UX in a user satisfaction survey.
Observability and Product Data
- Built an observability system based on crash, log, and behavioral (funnel/retention) data to drive product improvements.
- Built unified logging on Sentry + Crashlytics, reducing the time needed to identify the root cause of incidents.
- Linked analytics, session recording, and event logs by user identifier to lay the groundwork for funnel/retention analysis.
Web Operations and Deep Links
- Reliably handled complex entry/return flows with URL-based routing.
- Standardized the install/deep-link experience across iOS and Android using Universal App Links.
- Built a non-developer editing/publishing workflow that reduced content operations time.
Wegooli is a mobility startup that has developed a car-sharing platform for public housing residents, including Bucheon's Ministry of Land smart-city project, among others.
Flutter App Launch
- Led a rapid response to the existing app's Android SDK issues and the launch of a new Flutter app, improving overall app quality and performance.
Figma Design System
- Rapidly built a componentized UI on a Figma design system, cutting development time by more than 30%.
Gbike is a mobility startup that operates the electric kickboard sharing service 'GCOO' across 50 cities domestically and internationally.
Directly developed a React Native module that subscribes to real-time gait data computed from each device's supported sensors.
Gained performance-optimization experience by directly using modern native module architectures and performance-monitoring tools such as Turbo Module, Hermes, and Flipper.
Cross-Platform Pedometer Module
- Developed a native module that combines iOS's CMPedometer and Android's SensorManager to process step-count data in a unified way across platforms.
- Improved measurement accuracy by applying the AOSP step-detection algorithm to low-level accelerometer data, to support devices down to Android API 19.
- Built on a React Native Turbo Module-based architecture to reduce the JS-Native bridge bottleneck and improve response latency.
- Monitored and optimized memory usage and runtime behavior using Hermes/Flipper-based performance tracing.
Bside Korea is a shareholder-activism platform that lets minority shareholders in invested companies act together through shareholder verification, consolidation, and electronic signatures.
Cross-Platform Product Architecture
- Took part in overall development of the Flutter-based app and the RedWoodJS-based web app, understanding and implementing requirements on both the backend and mobile sides.
- The Flutter app was designed around proxy-voting delegation during the season, and automated shareholding verification and lounge-gathering features in the off-season.
- Implemented advanced data-integration features via Kotlin/Swift-based native functionality and a GraphQL API.
Electronic Proxy Voting
- Using Flutter, built a service that collects electronically-signed proxy votes from minority shareholders for a specific stock during a campaign and delivers their consolidated opinions to the asset manager through the shareholders' meeting.
- Built the main components using Flutter's Material UI and official packages, and implemented ID card photo capture, e-signature storage, and voting for proxy delegation.
- Over 1,500 users participated in the actual proxy-voting delegation process, recording an average user feedback satisfaction score of 4.5.
Native Authentication Integration
- Wrote native bridge code in Kotlin (Android) and Swift (iOS) to integrate with external scraping and the accredited-certificate (공인인증서) module.