Andrii Sirko Get in touch

Contracting at ABOUT YOU · open to conversations

Andrii Sirko

Senior Frontend Engineer Full-Stack Contractor

Ten years of React in production. I take on frontends that have to hold up — large monorepos, real traffic, and teams that need a system rather than a patch.

Years shipping
12
Engagements
13
Peak MAU
1M+
Markets served
90+

The ledger

What shipped,
year by year.

Every engagement since 2014 — the product, what was delivered, and the stack it ran on. Pick one to read the detail.

    Full engagement history, in text
    1. ABOUT YOU

      – Present

      Senior Frontend Engineer · Contract · Remote · aboutyou.de

      Customer-facing features in a large-scale React/TypeScript e-commerce monorepo powering the mobile and desktop web shops, with a gRPC data layer and container/presentational package architecture.

      • Delivered the loyalty Status Program end-to-end — gRPC client integration, deep-linked routing, mobile and desktop views — from API stub to production rollout inside the Coins wallet.
      • Extended the A/B testing infrastructure with dynamic activation of server-side experiments and shipped experiment winners; hardened the GA4-scale analytics layer by eliminating duplicate events and enforcing event-schema correctness.

      Stack React · TypeScript · Monorepo (Yarn workspaces) · Linaria · React Query · Zustand · gRPC · Storybook · Jest · RTL · Cypress · GitLab CI

    2. SelectCode GmbH

      Fullstack Developer · Contract · Remote · meingpt.com

      An enterprise-grade, privacy-focused AI platform with RAG capabilities and multi-LLM support.

      • Developed collaborative features — shared AI assistants and chat workflows — in React and Zustand.
      • Implemented secure TRPC/Prisma endpoints covering organization hierarchies, RBAC via Lucia Auth, and Stripe subscriptions.

      Stack TypeScript · React · NestJS · TRPC · Prisma · PostgreSQL · Playwright · RAG · OpenAI API · Kubernetes

    3. Mehrwerk GmbH

      Frontend Lead · Contract · Remote · mehrwerk.de

      Four years leading frontend for a loyalty and benefits platform, run alongside parallel contracts.

      • Led a team of 5 and architected a scalable React application framework that cut client onboarding from 4 months to 30 minutes.
      • Built a UI Editor for real-time content updates across web and native, serving 1M+ monthly active users.
      • Designed and owned the full load-testing suite — smoke, stress, soak and spike — for SSR and GraphQL services using k6 and Grafana Cloud.

      Stack TypeScript · React · Ionic · React Native · Next.js · Node.js · Kotlin · GraphQL · MongoDB · Jest · Cypress · AWS · k6

    4. eBay GmbH (Adevinta)

      Senior React Developer · Contract · Remote · kijijiautos.ca

      Dealer retail team on Kijiji Autos, Canada’s largest online auto platform.

      • Delivered React features across the dealer-facing product surface.

      Stack React · TypeScript · ESLint · Jest · TestCafe · AWS

    5. Accenture · smart / Daimler

      Senior React Developer · Contract · Remote · future.smart.com

      The smart IAA landing page for the brand’s future product reveal.

      • Implemented immersive, animated React components for a high-traffic automotive brand launch.

      Stack React · TypeScript · Styled Components · Webpack · AEM · Jest

    6. lemon.markets GmbH

      Senior React Developer · Contract · Remote · lemon.markets

      Blog and CMS surfaces for a fintech brokerage API product.

      • Built custom Prismic-powered slices for Blog and CMS pages.

      Stack React · Next.js · TypeScript · Prismic · ESLint · Jest

    7. Accenture · VW / Audi

      Senior React Developer · Contract · Remote

      White Label Dealer Search, shipped across two automotive brands.

      • Implemented a White Label Dealer Search app for VW and integrated it into Audi using a micro-frontend approach, supporting Audi.de across 90+ markets.

      Stack React · TypeScript · Styled Components · Webpack · Jest

    8. Factor Eleven

      Senior React Developer · Contract · Remote · factor-eleven.de

      AdManager platform and the component ecosystem around it.

      • Architected and implemented a React-based AdManager application and component ecosystem.
      • Built a shared UI library reused across multiple projects for consistency.

      Stack React · GraphQL · Apollo · Jest · Enzyme · Cypress · SASS · CSS Modules · Webpack · GitLab

    9. ToolTime

      Senior React Developer · Contract · Berlin · tooltime.de

      Field service management for tradespeople.

      • Designed and implemented a React-based field service management application.

      Stack TypeScript · React · GraphQL · Apollo · Jest · Cypress · CircleCI · AWS

    10. Careem

      Senior Software Developer · Full-time · Berlin · careem.com

      Corporate customers department at the Middle East’s largest ride-hailing platform.

      • Built React components and led architectural decisions for the corporate customers department.
      • Maintained a shared Web UI library used across the Careem ecosystem.
      • Contributed to LMD (last-mile delivery) and CareemNow (food delivery). Scrum master for a team of 6.

      Stack React · React Native · Redux · Saga · TypeScript · Jest · Cypress · Webpack · Kotlin · Scala · MySQL · AWS · Docker · Jenkins

    11. Circula GmbH

      Frontend Developer · Full-time · Berlin · circula.com

      Expense management for accountants and supervisors.

      • Built expense management tools for accountants and supervisors.

      Stack React · Redux · Ruby on Rails · RSpec · Docker

    12. Mes.mo GmbH / Gastroguide

      Full Stack Developer · Full-time · Stuttgart · gastroguide.de

      Seven products for restaurants, built end to end.

      • Architected a reservation system, website constructor, advertising system, file manager, form builder, menu builder and a REST API for mobile apps.

      Stack React · Redux · Flux · PHP · MySQL · AWS

    13. UKEESS

      Full Stack Developer · Full-time · Lviv, UA · cma.ua

      Where it started — e-commerce plugin work.

      • Developed and maintained Magento plugins for e-commerce clients.

      Stack Magento · PHP

    Selected work

    What actually shipped

    Six engagements where the outcome is easy to state. The rest are in the ledger.

    ABOUT YOU2026 — now

    A loyalty program, API stub to rollout

    Delivered the Status Program end-to-end inside the Coins wallet on a 40M+ MAU e-commerce platform — gRPC client integration, deep-linked routing, mobile and desktop views. Extended the A/B testing infrastructure with server-side experiment activation and hardened the GA4-scale analytics layer against duplicate events.

    • React
    • TypeScript
    • gRPC
    • React Query
    • Cypress

    Mehrwerk2021 — 2025

    Client onboarding: 4 months to 30 minutes

    Led a team of five and architected a React application framework that turned a four-month bespoke onboarding into a half-hour configuration. Built the UI Editor that pushes real-time content across web and native for 1M+ monthly active users.

    • React
    • Next.js
    • Ionic
    • GraphQL
    • k6

    Accenture · VW / Audi2020 — 2021

    One dealer search, 90+ markets

    A white-label Dealer Search built for Volkswagen, then integrated into Audi as a micro-frontend rather than a fork. Runs on Audi.de across more than ninety markets.

    • React
    • TypeScript
    • Micro-frontends
    • Webpack

    SelectCode2025 — 2026

    Private AI, with the boring parts done right

    Shared assistants and chat workflows for a privacy-focused enterprise AI platform with RAG and multi-LLM support — plus the unglamorous half: TRPC/Prisma endpoints for organization hierarchies, RBAC and Stripe subscriptions.

    • NestJS
    • TRPC
    • Prisma
    • RAG
    • Kubernetes

    Mehrwerk2021 — 2025

    Load tests that ran before the traffic did

    Designed and owned the full k6 suite — smoke, stress, soak and spike — against SSR and GraphQL services, reported through Grafana Cloud. Capacity questions got answered with numbers instead of opinions.

    • k6
    • Grafana Cloud
    • SSR
    • GraphQL

    Careem2018 — 2019

    A UI library the whole ecosystem used

    Led architectural decisions for the corporate customers department and maintained the shared Web UI library across Careem’s products, contributing to last-mile delivery and CareemNow. Scrum master for a team of six.

    • React Native
    • Redux Saga
    • Kotlin
    • AWS

    Stack

    Tools, and where they were used

    Pick anything below to see which engagements it came from — the answer appears in the ledger above.

    About

    Ten years, one discipline

    I’ve worked as a contractor for most of my career, which means I join codebases that already have history and constraints. The job is rarely a rewrite. It’s reading what’s there, finding the seam, and leaving the team with something they can extend after I’m gone.

    I’m based in Berlin, Germany, and work remotely across European time zones. Ukrainian is my first language; I work in English and German.

    Education

    Lviv Polytechnic National University

    MSc Computer Science · 2010 — 2015

    Thesis: a context-aware web service for booking personal services. Coursework included writing a compiler in C/Assembler and implementing virtual desktops for Windows 7 against the WinAPI.

    Languages

    • Ukrainian Native
    • English Fluent · B2
    • German Fluent · C1

    Away from the keyboard

    • PowerliftingCandidate Master of Sport
    • Reading25+ books a year
    • Travel30 countries
    • AlsoMotorcycling & 3D printing

    Contact

    Have something that
    needs to hold up?

    Contract, fractional lead, or a second opinion on an architecture decision — all fine.

    Berlin, Germany · remote across Europe · CV in plain text