Андрій Ветеран

Andrii Kosaniak
Senior Full-Stack Engineer Full-Stack Engineer with 6+ years of commercial experience in React and Node.js with
React + Node.js TypeScript. Delivers features end to end, from React/Next.js interfaces to the NestJS and
[відкрити контакти](див. вище в блоці «контактна інформація») Express services behind them, working with PostgreSQL, WebSockets and RabbitMQ on
[відкрити контакти](див. вище в блоці «контактна інформація») the backend. Supports released products: triages production issues through Datadog,
Villajoyosa, Spain Grafana and Sentry and ships fixes through GitHub Actions and Azure DevOps pipelines.
Remote, CET time zone Uses Claude Code and Cursor daily, reviewing and testing what they generate before
English C1 merge. Comfortable picking up unfamiliar and legacy code, working on several products in
parallel and communicating directly with product managers, designers and QA.

Technical Skills
Frontend: React, Next.js (App Router), TypeScript, JavaScript (ES6+), HTML5, CSS, Tailwind CSS, Styled Components, Storybook,
Recharts, Responsive Design, Accessibility
State & Data Fetching: Redux, React Context, TanStack Query, Zustand, MobX, React Hook Form, Axios
Backend: Node.js, NestJS, Express.js, REST APIs, WebSockets, RabbitMQ, BullMQ
Databases: PostgreSQL, MongoDB, Redis, MikroORM, Prisma, Mongoose, Supabase
CI/CD & Cloud: GitHub Actions, Azure DevOps, Docker, Docker Compose, Kubernetes, AWS, Vercel, Netlify, Heroku
Observability: Datadog, Grafana, Sentry, Chrome DevTools
Testing: Vitest, React Testing Library, Playwright, Jest, Supertest, ESLint
AI Tools: Claude Code, Cursor, ChatGPT, Gemini API
Practices: Code Review, Legacy Refactoring, SOLID, Layered Architecture, Agile, Scrum, Mentoring

Experience
DivFlow LLC
Senior Full-Stack Engineer Jun 2025 - Present
SaaS subscription and billing tools, developed in parallel for 5 client products.
• Built React/TypeScript subscription configuration and billing screens, including invoice search, balance views and downloads, with
typed REST contracts, clear loading and error states and protection against stale responses after filter changes.
• Developed shared components used across the 5 products, documented in Storybook, and reduced the subscription purchase funnel
from 6 steps to 3 through UX iterations and Amplitude-based A/B tests.
• Extended NestJS services for PostgreSQL-backed subscription workflows (MikroORM), added WebSocket events for real-time
updates and made RabbitMQ consumers safe to retry by storing processed message IDs in the same transaction.
• Monitored services with Datadog and Grafana, using metrics and logs to investigate production issues and confirm fixes after release.
• Used Claude Code and Cursor daily for implementation, reviewing generated changes before merge; covered key flows with Vitest,
React Testing Library and Playwright on the frontend and Jest on the backend.
• Maintained GitHub Actions pipelines and Docker builds for testing and deployment to Kubernetes, with Docker Compose for local
development.
Stack: React, Next.js, TypeScript, MobX, Storybook, Node.js, NestJS, MikroORM, PostgreSQL, RabbitMQ, WebSockets, Datadog, Grafana,
Vitest, Playwright, Jest, GitHub Actions, Docker, Kubernetes

Synergist Technology
Frontend Engineer / UI Lead Mar 2024 - May 2025
AI monitoring platform with interactive React dashboards; UI Lead in a 5-person team.
• Built the Next.js/TypeScript interface of the platform, defining reusable screen structures and keeping layouts, API access and
component behavior aligned with product and design.
• Profiled Recharts rendering and data fetching with Chrome DevTools to find slow updates and unnecessary requests during
dashboard interaction.
• Separated TanStack Query server state from Zustand UI state and cancelled outdated filter requests, so views stayed consistent
while users changed inputs.
• Extended Node.js/NestJS reporting endpoints with new filters, validation and BullMQ export jobs when dashboard features needed
backend changes.
• Developed Storybook chart and data-grid components for more than 10 dashboard views; shipped changes through Azure DevOps
pipelines and tracked frontend errors in Sentry.
Stack: React, Next.js, TypeScript, Tailwind CSS, TanStack Query, Zustand, Recharts, Storybook, Node.js, NestJS, BullMQ, Azure DevOps,
Sentry

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JobBuffer GmbH
Full-Stack Developer Dec 2022 - Feb 2024
CV builder and job-posting platform with editable document templates and dynamic pages.
• Built CV-builder interfaces with Next.js, TypeScript and Tailwind CSS, focusing on responsive layouts, cross-browser behavior and
editable document workflows.
• Implemented configurable job-posting templates with dynamic page structures, coordinating navigation and document editing
through DOM events and URL state.
• Refactored legacy JavaScript Express code into typed modules covered by Jest regression tests; maintained MongoDB/Mongoose
models and Docker releases to AWS.
Stack: React, Next.js, TypeScript, Tailwind CSS, Node.js, Express.js, MongoDB, Mongoose, Jest, Docker, AWS

Cursor.Education
JavaScript / React Mentor (Part-Time) Sep 2022 - Nov 2022
Part-time JavaScript/React mentoring with code reviews and live debugging.
• Mentored 15 students in JavaScript, CSS and React, reading and debugging their code in live sessions and reviews; 12 of them
published their first web applications.
Stack: JavaScript, CSS, React, Code Review

ROLIQUE
Full-Stack Developer Jun 2020 - Nov 2022
Client SaaS applications with React interfaces and Node.js integrations.
• Integrated more than 10 third-party REST APIs through Node.js/Express adapters into a React/Redux application, validating external
payloads before passing them to the UI.
• Built real-time features over WebSockets between Express backends and React clients.
• Delivered a SaaS MVP extension over 5 months with TypeScript, Express, Prisma/PostgreSQL and React/Tailwind; used Docker
Compose locally and released on Netlify and Heroku.
Stack: React, Redux, TypeScript, Tailwind CSS, Node.js, Express.js, Prisma, PostgreSQL, WebSockets, Docker Compose, Netlify, Heroku

Selected Project
AI Lab-Analysis SaaS for Veterinary Clinics
Founder & Developer (own product)
Seat-based SaaS that helps veterinary clinics read and interpret lab results with an LLM.
• Built and run independently: Gemini API (Gemini 2.5 Flash) for OCR-based lab result reading and AI case interpretation, seat-based
billing with WayForPay, a Supabase/PostgreSQL backend, analytics and an epizootic surveillance map.
Stack: Gemini API, Supabase, PostgreSQL, WayForPay

Education
Ivan Franko National University of Lviv
Bachelor of History
Okten School
JavaScript Complex (Full-Stack Course)

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