Andrii Sirko Get in touch

Wrapping up at ABOUT YOU · open for the next contract

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.

Get in touch See the ledger
Years shipping
12
Engagements
13
Peak MAU
40M+
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

      –

      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.

      • Built the frontend of a new loyalty Status Program inside the Coins wallet — gRPC stub layer ahead of the backend, feature module, deep-link routing, skeleton loading and a pixel-matched glass-card design system — covered with Storybook and integration tests; handed over in final review.
      • Built a Figma-to-code icon migration pipeline (Node.js, Figma REST API) that replaced ~120 shared icons with zero call-site changes.
      • Delivered the mobile add-to-basket CTA experiment end to end — SSR for multi-size products, size selection, captcha retry, accessibility — with Cypress E2E and integration tests.
      • Replaced per-experiment feature flags with prefix-based A/B activation, cutting frontend config work per new experiment to zero; rolled out winners.

      Stack React · TypeScript · Linaria · gRPC · Monorepo (Yarn workspaces) · Node.js · Storybook · Jest · RTL · Cypress · GitLab CI · Datadog

    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.
      • Led the WCAG accessibility migration across the platform — audited components, defined remediation standards, and drove implementation to compliance across web and native apps.

      Stack TypeScript · React · Vue 2/3 · 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) on a platform handling 380M+ requests a day for 10M+ monthly active users. 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

    A loyalty program, API stub to handover

    Built the Status Program frontend inside the Coins wallet on a 40M+ MAU e-commerce platform — a gRPC stub layer ahead of the backend, deep-linked routing, skeleton loading and a pixel-matched glass-card design system, covered by Storybook and integration tests. On the side: a Figma-to-code pipeline that swapped ~120 shared icons with zero call-site changes, and prefix-based A/B activation that took per-experiment config work to zero.

    • React
    • TypeScript
    • gRPC
    • Storybook
    • 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 — a platform handling 380M+ requests a day for 10M+ monthly active users. Scrum master for a team of six.

    • React Native
    • Redux Saga
    • Kotlin
    • AWS

    Live demo

    Ask the CV a question.
    Watch the page answer.

    A voice agent that knows this CV and drives the UI while it talks — a small, production-shaped ElevenLabs Agents integration in a real React app.

    Ask “What did Andrii build at Mehrwerk?” and the matching project card lights up on screen. The agent answers from a RAG knowledge base over the CV. The browser never sees an API key: a Next.js route mints a short-lived signed URL, throttled per IP, and the session opens over WebSocket from there.

    There is a text mode, so no microphone is needed. The agent, its tools and the knowledge base are code in the repo, pushed with the ElevenLabs CLI, with unit tests on the tool handlers, transcript and throttle.

    Open the demo Read the source
    • Next.js
    • TypeScript
    • ElevenLabs Agents
    • RAG
    • Tailwind
    • Vitest
    • Vercel

    Client tools the agent can call

    highlightProject{ projectId }
    Scrolls to the project card and highlights it. Blocks until the UI confirms, so the agent says what actually happened.
    filterByTech{ tech }
    Filters the grid by stack and returns the match count — “three projects used GraphQL” comes from the DOM, not the model.
    showContactno params
    Reveals the contact panel.

    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 · C1
    • 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. Or skip the email and ask the voice agent.

    Phone +49 176 4340 4914 Call LinkedIn in/andrii-sirko Open GitHub andrii-sirko Open

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