Valentyn H.

I build React Native apps that start fast, work offline, and ship fixes the same day, with no waiting on app-store review. I also audit existing apps and tell you, in plain writing, what's solid, what's risky, and what it will take to fix. 11 years in mobile, with native iOS (Swift) and Android (Kotlin/Java) expertise. Recent results for clients and employers: • Cut screen load times ~6x (3s → 0.5s) for a field-service app used in low-connectivity environments • 3x faster app startup and 20% smaller binaries for a US automotive OEM's companion app (led a team of 10) • Migrated a production app from bare React Native to Expo/EAS, so most changes now ship as same-day OTA updates • Built offline-first sync architectures (Realm, WatermelonDB) with zero data loss on flaky networks What I can do for you: • Audit an existing app or assess an Expo migration. A written report with ranked issues and a phased plan will be provided if needed • Build a new React Native app: architecture, UI, and releases to both stores • Modernize an existing app: performance profiling, New Architecture (Fabric/TurboModules/JSI), Expo migration • Write native modules in Swift/Kotlin and bridge them to React Native: BLE devices, background uploads, maps, anything the JS layer can't do • Add on-device camera scanning: barcodes, QR codes and OCR for serial numbers and other printed IDs (VisionCamera + ML Kit) • Add in-app purchases and subscriptions on iOS and Android • Set up CI/CD: GitHub Actions, Fastlane, EAS Build/Update, phased store rollouts, crash monitoring (Sentry, Datadog, Crashlytics) • Set up an agentic AI workflow (Claude Code) for your team, so routine migration and cleanup work goes faster with a developer reviewing every change How I work: I communicate proactively, flag risks early, and say so when something in your codebase needs challenging. I use Claude Code daily across mobile, backend, and CI/CD, so routine work goes faster and your budget goes to senior architecture and review, not boilerplate hours. Stack: React Native (New Architecture), Expo/EAS, TypeScript, Swift, Objective-C, Kotlin, Java, Redux/Zustand, Realm, WatermelonDB, VisionCamera, ML Kit, Firebase, Jest, Detox, Maestro, Node.js, Next.js. If you need a senior mobile engineer for a build, a rescue, or an honest second opinion on the app you have, send me a message and let's talk about it.