Serhii

SERHII SIEDNIEV
Middle+ Frontend Developer (React / Next.js / TypeScript)
[відкрити контакти](див. вище в блоці «контактна інформація») | [відкрити контакти](див. вище в блоці «контактна інформація») | Telegram: @serhiisiedniev | Zaporizhzhia, Ukraine
github.com/smoke-flame | [відкрити контакти](див. вище в блоці «контактна інформація»)

SUMMARY
Middle+ Frontend Developer with 4.5+ years shipping production React/Next.js applications in fintech, construction-tech and e-
commerce. Track record of measurable impact: cut a core workflow by 63% with a custom Chrome extension, dropped bug-
detection time by 42% through observability tooling, and pushed booking conversion up double digits via performance and UX
fixes. Comfortable owning a feature from architecture to API integration as sole frontend or within a small Agile team. Now
extending into backend with Node.js/Nest.js to work full-stack across the API layer.

SKILLS
Languages: JavaScript, TypeScript, HTML5, CSS3, SCSS, JSON, Markdown
Frontend: React, Next.js, React Router, Redux, Redux Toolkit, React Query, Formik, React Hook Form, Zod, Tailwind CSS,
Bootstrap, Material UI, shadcn/ui, Styled Components, Vue.js, Vuex, Vue Router, Vuetify, Alpine.js, jQuery, Highcharts, Chart.js,
React Native, Expo, Apache Cordova
Backend (in progress): Node.js, Express.js, Nest.js, Microservices Architecture, RabbitMQ, Prisma (ORM), REST API, WebSockets,
OpenAPI, OAuth 2.0, JWT
Databases: MongoDB, PostgreSQL
Tools & Workflow: Git, GitHub, GitLab, Bitbucket, Webpack, Vite, Babel, ESLint, Prettier, Docker, Docker Compose, GitLab CI/CD,
GitHub Actions, Sentry, Figma, Notion, Slack, Jira, Confluence, Trello, Agile/Scrum, BDD, MVC/MVVM, Performance Optimization,
Clean Code & Refactoring

WORK EXPERIENCE

Front-End Developer — Drum'n'code Aug 2021 – Present
Furnishing Platform
• Shipped a Chrome extension that lets users pin furniture from any site in two clicks with auto-filled price, title and image —
cut product-add time by 63.4% and lifted saved items per active user by 27.9%.
• Rolled out Sentry alerting with session replay across critical UI flows, shrinking mean time-to-detect frontend issues by 41.6%
and dropping user-reported bugs by 18.3%.
• Replaced classic pagination with responsive infinite scroll across search, growing items viewed per session by 22.7% while
holding Core Web Vitals steady.
• Profiled and fixed rendering bottlenecks in the new catalog layout, cutting layout-shift incidents by 31.2% and eliminating
scroll jank.
Technologies: React, Redux, Material UI, Sentry

Construction Projects Dashboard
• Owned end-to-end delivery of a search experience combining autocomplete, a nested category tree and live map sync,
cutting time-to-find a relevant project from 4–5 minutes to 1.6 minutes.
• Architected an auth and subscription layer gating premium data behind paid access, lifting paid conversion by 15.4% with no
measurable performance cost.
• Introduced virtualized scrolling for search results and map lists, slashing memory usage by 49.8% and cutting long-task
occurrences by 36.9% on heavy queries.
• Diagnosed and resolved Leaflet map performance issues, dropping interaction latency by 28.5% and lifting internal
satisfaction scores.
Technologies: React, TypeScript, Tailwind CSS, MobX, Leaflet

Payment System (Cards + Crypto)
• Led front-end architecture for merchant and internal-operator dashboards, standardizing reusable layout and form patterns
that cut time to ship new reporting or settings pages by 33.1%.
• Delivered OpenID authentication with fine-grained, role-based access at store, wallet and action level — drove unauthorized
access incidents to zero and cut 'wrong access level' tickets by 24.7%.
• Engineered withdrawal and balance-management flows with granular permissions and a balance-hiding mode, reducing
operational errors in financial actions by 19.3% and sharpening audit clarity.
• Localized the app by browser language and hardened form validation with React Hook Form, boosting non-English
onboarding completion by 14.6% and cutting submission errors by 21.8%.
Technologies: React, TypeScript, Tailwind CSS, OpenID, AG Grid, Sentry, i18n, Axios, React Hook Form

US Wedding Agency Platform
• Migrated the UI to shadcn/ui and Tailwind CSS, unifying booking-flow design and pushing component reuse up 37.2%.
• Redesigned the booking journey into a multi-step form, cutting average completion time from 6.2 to 3.9 minutes.
• Enforced schema-level validation with Zod, dropping invalid submissions by 23.5% and reducing support back-and-forth over
bad requests.
• Tuned Next.js delivery via code splitting and image optimization, raising Lighthouse performance from 81 to 94 and lifting
mobile completion by 9.8%.
Technologies: React, Redux Toolkit, TypeScript, Next.js, Tailwind CSS, shadcn/ui, Zod

EDUCATION
Ukrainian State University of Science and Technologies

LANGUAGES
English — Upper-Intermediate (B2)