Denys Bohatyrchuk

- Shipped all 4 payment rails (card, Apple Pay, Google Pay, and Poland's BLIK) into an Expo banking app despite the vendor shipping no React Native SDK, by building a custom native Expo module wrapping Checkout.com's iOS and Android SDKs with a typed JS bridge (~60% native Swift/Kotlin). - Removed ~30% duplicated code across 3 company projects, by extracting shared layers — typed API client, money-precision arithmetic, design tokens, and utilities — into reusable libraries adopted company-wide. - Established a single source of truth for API clients, by building the full OpenAPI codegen pipeline from scratch as my own initiative. - Built the team's entire CI/CD pipeline from zero: quality gates, test runs with reporting, AI-assisted code and security review, branch policies, and namespace-aware publishing that releases only the changed module. - Cut code-review overhead, by adding automated AI review (Rovo) at the PR stage and a script that auto-generates PR templates (title, description, change summary) via the GitLab API.

- Architected a TypeScript monorepo (pnpm + Turborepo) powering 4 client apps — manager, dispatcher, and driver web clients plus React Native (Expo) apps — from shared design-system and data-layer packages, as founding engineer authoring ~74% of commits (3× the next contributor). - Eliminated frontend/backend contract bugs by building a contract-first API layer auto-generating 130+ typed models and 12 service clients from an OpenAPI spec, with React Query hooks and optimistic cache updates. - Built a real-time dispatch experience tracking many moving vehicles on a live map, by combining WebSockets (with exponential-backoff reconnection) and Google Maps with marker clustering, routing, and geocoding. - Handled background location tracking with restart-time polling and background push notifications, by integrating native location and Firebase Cloud Messaging so drivers' key-point arrivals and status changes surfaced without the app open. - Kept the live map smooth under high-frequency updates, by batching socket events into a buffer flushed on fill or every 5s, instead of re-rendering per message.

- Led a 3-person mobile team on a production app operated by police personnel, by owning technical direction: library-vs-build decisions, incremental refactor strategy (legacy React → modern), branch policy, and code review. - Brought a Xamarin developer to full autonomy in ~2 months, by mentoring them through the React Native transition and mobile-specific architecture, after which they shipped independently. - Met a strict no-open-source security mandate for a police-operated app, by implementing a custom native audio manager in Swift/Obj-C rather than third-party libraries. - Enabled officers to control hardware without opening the app — mute/unmute, switch output source — by implementing BLE and wiring it into iOS audio routing across up to 3 devices (Flic button, walkie-talkie, headset). - De-risked releases on a live public-safety app, by introducing percentage-based rollouts and feature flags so changes could ship incrementally and roll back safely.

- Built offline-first functionality covering ~70% of the app for rural, low-connectivity users, by implementing local storage (MMKV), offline optimistic updates, and a persisted query queue replayed on reconnect with capped retries. - Sustained stability across a large monorepo where multiple apps shared modules, by raising test coverage to ~90% (Jest) to catch side-effect regressions during feature work. - Contributed cross-platform features (React, Next.js, React Native) to a production agritech platform serving a large smallholder-farmer base, as a senior IC in a ~20-engineer org.

- Brought Telegram messaging into a React Native app with no prior art to reference, by independently researching and building a C++→native bridge: compiling TDLib via CMake into dynamic libraries and exposing a native interface with JS-side callbacks (~75% native C++/Swift/Java work). - Powered on-chain trading, royalties, and NFT lotteries across 3 blockchains (Ethereum, Velas, Solana), by implementing 5 smart-contract integrations — ERC-20/721/1155, an escrow-based royalty contract, and a subscription contract. - Built an NFT minting and staking web app solo in ~3 weeks, and contributed to the team-built crypto wallet, by developing test-first with Web3.js. - Eliminated scroll jank across the app's many list-heavy screens (feeds, chats, token and transaction lists), raising scroll performance from ~15 FPS drops to a steady 60 FPS, by replacing list rendering with a RecyclerListView wrapper that enforces item sizing to optimize React Native's virtualization. - Standardized icon usage codebase-wide, by building a type-safe Icon component (Strategy pattern) that parses the icon folder into a TS union type, rejecting invalid names at compile time. - Owned the entire native layer for an app that reached 10K daily active users, as the sole engineer responsible for native integration.

- Shipped 2 production banking/fitness apps for African markets, by building offline USSD banking flows, a native AcquireSDK bridge (Java/Swift) for PCI-compliant payments, and a persistent Android Headless.js background service that streams sensor + biometric data to compute activity metrics with the screen off.

- Built web and mobile features for a music-distribution platform in a monorepo, including an interactive SVG world map (React Native Reanimated) visualizing per-country play statistics, with business logic covered by Jest.

- Built language-learning features across mobile and web — interactive lesson flows, multimedia exercises, final tests, and a three-tier in-app subscription system.