Viktor

Viktor Kolesnyk
Senior Full-Stack Engineer · React, Node.js & React Native
Vienna, Austria · [відкрити контакти](див. вище в блоці «контактна інформація») · [відкрити контакти](див. вище в блоці «контактна інформація») · [відкрити контакти](див. вище в блоці «контактна інформація»)
Eligible to work in the EU · Open to fully remote roles (EU / US time zones)

PROFESSIONAL SUMMARY
Senior full-stack engineer with 7 years building production web and mobile applications — React, Next.js, and
React Native with TypeScript on the client; Node.js (Express, NestJS) and PostgreSQL on the server. Currently
building an AI-powered audit platform on an AWS-based stack: RAG over company documents and open data
sources, structured LLM outputs, cost-controlled AI / LLM API integrations, and frontend architecture end-to-end.
Background across fintech/crypto, marketplace, social-tech, and SaaS — including payments (Stripe, Amazon
Payment Services), real-time features, and enterprise dashboards. Architect React Native apps from the ground
up for iOS and Android, mentor mid-level engineers, and use AI-assisted development (Cursor, Claude Code) to
ship faster in fully English-speaking, distributed teams.

SKILLS
Languages: TypeScript, JavaScript (ES6+), HTML5, CSS3 / SCSS
Frontend: React, React Native, Next.js, Redux, Redux Toolkit, Redux-Saga, React Query, Zustand, React
Navigation, React Native Reanimated, Material UI, Styled Components
Backend & Data: Node.js (Express, NestJS), REST APIs, GraphQL, WebSocket, PostgreSQL, Firebase
Testing & Tooling: Jest, Storybook, i18next, Git
Cloud & DevOps: AWS, Docker, GitHub Actions, GitLab CI
Integrations: AI / LLM APIs, Stripe, Amazon Payment Services, Salesforce
Practices: Mobile & web architecture, design systems, design patterns, Agile / Scrum, code review, mentoring,
AI-assisted development (Cursor, Claude Code)

WORK EXPERIENCE
Senior Full-Stack Engineer Feb 2026 – Present
Dea.io — AI-powered platform for auditing companies across the EU — Germany / Austria
• Own the platform end-to-end across frontend and backend — React, Next.js, and TypeScript on the client;
Node.js / Express services and databases on an AWS-based stack — from the component system through
APIs, deployment, and performance optimization.
• Design and build the AI core of the product: RAG pipelines over company documents and open data sources,
structured LLM outputs feeding audit workflows, and per-request cost controls across multiple AI / LLM APIs.
• Delivered the MVP, now in closed production use with a large enterprise client in Germany / Austria.
• Accelerate delivery with AI-assisted development tools (Cursor, Claude Code) embedded in the workflow,
shipping features faster while keeping the codebase clean and maintainable.
Senior Web & Mobile Engineer Feb 2023 – Dec 2025
AlMaal — Saudi fintech startup; two products on a blockchain / crypto platform — a consumer investment app and a
B2B business-banking portal
• Architected and built two first-of-their-kind fintech products from the ground up for the Saudi market — a
consumer investment app and a B2B business-banking portal — across web (Next.js, React, Material UI) and
mobile (React Native for iOS & Android), including native modules where React Native fell short.
• Owned frontend architecture and optimization end-to-end, and built real-time functionality over WebSocket:
live pricing, interactive dashboards, and a support chat blending live agents with AI.
• Integrated Amazon Payment Services for in-app card payments (the region's Stripe equivalent) and
Salesforce for CRM; managed Android / Google Play release workflows and analytics with Firebase.
• Led tech-stack selection and migration and mentored 2–3 mid-level engineers within a team of up to 10,
through code review and pair programming.
Middle–Senior Web & Mobile Engineer Nov 2021 – Jan 2023
Nestozo — US marketplace for booking home services (repairs, cleaning, interior design)

• Architected and shipped iOS and Android apps for booking home services, scaling to 10K–100K monthly
active users.
• Built Next.js client portals and an admin panel managing relationships with dozens of recurring service
providers.
• Designed Redux-Saga state management for complex async flows, keeping the UX consistent under heavy
load.
• Integrated Stripe for customer payments and provider payouts; handled Android / Google Play release and
analytics with Firebase.
• Tuned performance for high-traffic conditions and maintained full Jest test coverage, working closely with QA.
Middle Web, Backend & Mobile Engineer Aug 2020 – Oct 2021
SWPro — UK social-technology product
• Built responsive web interfaces (React / Next.js) and React Native mobile features.
• Designed OAuth 2.0 / JWT authentication and authorization and secured API integrations.
• Built WebSocket-based real-time messaging across clients, servers, and background workers.
• Developed supporting backend services in NestJS with PostgreSQL; documented UI components in
Storybook and ran code reviews and pair programming in Agile sprints.
Junior–Middle Web & Backend Engineer Apr 2019 – Jul 2020
Quolio — Ukraine-based B2B SaaS
• Built React and Material UI front-end components and documented UI patterns in Storybook.
• Developed GraphQL and REST APIs with Express.js and optimized PostgreSQL schemas, speeding up key
endpoints by 3–4×.
• Wrote unit tests and contributed to code reviews within an Agile framework.

EDUCATION
MSc in Computer Science 2024 – 2026
State University of Information and Communication Technologies (DUIKT) — Kyiv, Ukraine
BSc in Computer Science 2019 – 2023
Igor Sikorsky Kyiv Polytechnic Institute (NTUU “KPI”) — Kyiv, Ukraine

LANGUAGES
English — full professional working proficiency; daily working language in distributed teams since 2020 ·
Ukrainian — Native