- Achieved 5x user growth (100+ to 500+ active users) and facilitated 300+ NFT transactions over 12 months by delivering marketplace features: advanced filtering, P2P NFT lending, collection offers, and raffle mechanics with TON blockchain integration - Reduced bundle size by 33% and improved list rendering performance by implementing infinite scroll optimization and efficient API request patterns for NFT collections - Accelerated release cycle from bi-weekly to weekly by establishing code review standards, release branching workflows, and production monitoring with Sentry - Led frontend architecture in cross-functional team (2 FE, 1 BE, 1 QA, 1 Designer): owned technical decisions, complex Web3 transaction flows with Tonkeeper wallet integration, and task breakdown Tech: React, TypeScript, MobX, Vite, SCSS, TON Connect, Sentry

- Increased user engagement by 1.5x (lessons watched per user) and achieved 58% Video tab adoption rate by implementing carousel autoplay previews with AVPlayer prefetching and 8 interactive exercise types in Words tab, serving 20K+ active learners - Boosted user retention by 15% by building speech evaluation feature with real-time per-word correctness highlighting using SFSpeechRecognizer and AVAudioSession audio capture - Improved app stability from 90% to 95% crash-free rate and maintained 4.9 App Store rating by implementing robust error handling in media playback and speech recognition flows across bi-weekly releases Tech: Swift, UIKit, AVPlayer, SFSpeechRecognizer, AVAudioSession, UICollectionView (prefetching), Backend API integration

- Achieved 10% subscription conversion rate, generated 100+ paid subscriptions, and increased revenue by 1.5x by implementing end-to-end in-app purchase flow with react-native-iap, paywall UX, free trial, and cross-platform purchase restoration - Enabled offline-first functionality for 500+ users by building SQLite-Firestore sync mechanism with 99% success rate, allowing speech assistance features to work without internet connectivity - Reduced app size by 20% and improved stability (maintained 4.4 rating) by upgrading React Native 0.58 → 0.61 and resolving compatibility issues across bi-weekly releases Tech: React Native, JavaScript/TypeScript, Redux, SQLite, Firebase (Firestore, Analytics), react-native-iap