Kyrylo Sotnykov

Senior Full-stack Developer

• →Designed and implemented Keyper Vault, a non-custodial mobile wallet supporting Polygon, Ethereum, and Bitcoin networks with ERC-20/721/1155 and BTC assets.
• →Built secure authentication with email/Google/Apple OAuth, TOTP-2FA, backup codes, and WalletConnect.
• →Developed NestJS-based microservices with Nx monorepo, RabbitMQ messaging, PostgreSQL, Redis caching, and Prometheus/Grafana monitoring.
• →Configured HSM for key storage and encryption of mnemonics; implemented in-house KMS for development/test environments.
• →Built Airlock — a public Web3 platform automating memecoin distribution via configurable smart contracts.
• →Delivered MedEx MVP, a tokenization platform for insurance payouts in the US market — developed from scratch to near-production state, including backend, dashboards, and Solidity contracts.
• →Wrote and tested Solidity smart contracts for multi-type token issuance, distribution, and automatic USDC redemption.
• →Created a GameFi rental service for temporary asset lending with automated payments and returns.
• →Implemented signed API request verification using asymmetric cryptography for secure cross-service communication.
• →Designed microservices for auth, wallet, transactions, subscriptions, WebSockets, notifications, and uploads.
• →Built frontend dashboards in React + Tailwind CSS and mobile apps in React Native, ensuring consistent state management via Redux Toolkit, redux-persist, and live data via WebSockets.
• →Integrated Swagger auto-generated TypeScript clients, React Hook Form validation, and error-handling middleware for API calls.
• →Set up CI/CD pipelines in GitLab with Docker builds, linting, unit tests, and manual staging/production deployments through Terraform-managed IBM Kubernetes clusters.
• →Developed an RPC Proxy in NestJS + Redis to cache blockchain node queries, cutting RPC costs by 3×.
• →Monitored stability and transaction flow via Prometheus alerts, Grafana dashboards, and Slack notifications.
• →Collaborated in a 9-member cross-functional team (Tech Lead, backend/frontend/full-stack engineers, QA, blockchain developers, PM, designer) under Scrum → Kanban transition.

Senior Full-stack Developer

• →Developed a Web3 platform enabling multi-level access for users, managers, and admins — including transaction approval workflows, AML policy enforcement, and role-based dashboards.
• →Built the transaction policy module, allowing admins to define whitelisted recipients, transaction limits, time-based rules, and required approval thresholds.
• →Implemented offline transaction signing with locally stored, encrypted keys in secure-storage for non-custodial integrity.
• →Added biometric verification (Face ID / Touch ID) as mandatory authentication for signing transactions, with PIN fallback.
• →Used BIP-39, ethers.js, and web3.js for seed generation, wallet derivation, and transaction handling.
• →Designed and deployed a custom Key Management System (KMS) for encrypted mnemonic handling and integrated IBM HSM for production-grade secure key storage.
• →Built and maintained core backend services (auth, wallet, approval, policy) within a NestJS monolith, incorporating RabbitMQ for messaging and fault isolation.
• →Improved backend throughput using Redis caching and async message queues for stable concurrent performance.
• →Automated infrastructure with Docker, GitLab CI/CD, and multi-environment setup for reliable AWS deployments.

Middle Full-stack Developer

• →Implemented linting, unit, and end-to-end test gates in CI/CD pipelines to enforce code quality and prevent regressions.
• →Integrated Sentry for real-time error monitoring (dashboard and mobile) and CloudWatch for API-level observability.
• →Collaborated with the team through mutual code reviews and architecture discussions with the Tech Lead to ensure scalability and consistency across services.
• →Developed from scratch the Guardian Groups mobile app — a secure recovery system based on Shamir’s Secret Sharing, where 3–5 guardians approve requests to reconstruct sensitive secrets (mnemonics, passwords).
• →Built a React Native app with WalletConnect, encrypted mnemonic storage and native Swift/Kotlin integrations.
• →Designed and implemented the supporting NestJS API using BullMQ for queueing/retries, Prometheus + Grafana for metrics and logs, ensuring fault-tolerant backend operations.
• →Published and maintained the app on public marketplaces, covering the full delivery cycle from development to release.

Middle Full-stack Developer

• →Built modules for document generation, digital signing, and authentication in a monolithic Node.js + Vue.js architecture.
• →Integrated Cypher API to enable secure Ukrainian e-signature workflows for internal financial acts and documents.
• →Automated document lifecycle — from template generation to signature validation and storage.
• →Implemented PDF generation and metadata injection based on dynamic business data.
• →Ensured secure authorization and streamlined user flow for internal employees (no role hierarchy).
• →Managed 2 developers, distributed tasks, and maintained sprint-based delivery to meet deadlines.
• →Delivered a separate internal employee directory system using ElasticSearch for advanced search and filtering by manager and department.
• →Reduced document approval and processing time significantly after digital workflow adoption.

Middle Front-end Developer

• →Implemented real-time updates using GraphQL Subscriptions and a custom RTC Rust package.
• →Built a dynamic message history with infinite scroll and caching for optimized UX.
• →Enabled seamless transition of audio/video calls from tab to separate window without connection loss via link query and localStorage.
• →Integrated WebRTC-based modules for audio/video streaming and synchronized state updates.
• →Collaborated with backend team on GraphQL schema design and API integration.
• →Reviewed team code and maintained architectural consistency across components.
• →Used internal analytics tools to monitor performance and optimize client behavior.

Middle Front-end Developer

• →Built dynamic panoramas using Fabric.js with hotspots, markers, descriptions, and pricing.
• →Implemented floor selection, apartment filtering, and 3D navigation features.
• →Applied lazy loading and dynamic components to handle large textures and improve performance.
• →Integrated Clarity heatmaps for early UX feedback and navigation behavior analysis.

Middle Front-end Developer

• →Built responsive web apps using HTML/CSS/JS, jQuery, Bootstrap, transitioning to Vue.js & Nuxt.js
• →Developed an e-commerce platform with Nuxt.js + Node.js, LiqPay payments, and CRM integration
• →Delivered a PWA for car-rental admin panel with Service Workers, offline cache, and queued API sync
• →Implemented vuex-persist for state persistence and IndexedDB caching for offline use cases

Junior Front-end Developer

• →Optimized UX & SEO via Lighthouse audits, WCAG practices, and lazy-loading images (+~15% conversions)
• →Tested mobile/offline UX via Chrome DevTools & device emulation; deployed using Gulp pipelines
• →Collaborated closely with designers & backend team to ensure rapid, high-quality delivery