Serhii

Serhii Siedniev Email: [open contact info](look above in the "contact info" section)

Phone: [open contact info](look above in the "contact info" section)

Telegram: @serhiisiedniev

GitHub: smoke-flame

FRONT-END DEVELOPER Linkedin: [open contact info](look above in the "contact info" section)

ABOUT
Frontend Developer with 4.5+ years of experience delivering product-focused web applications across
interior design, construction, fintech/payments and service businesses. I focus on building real user
flows rather than static pages, from Chrome extensions that let users import products in two clicks, to data-
heavy search dashboards with maps and virtualized lists, to multi-role payment portals and booking flows
that feel predictable and easy to use.

My core stack is React, Next.js, TypeScript, Tailwind and modern front-end tooling, and I’m used to
working in small Agile teams or as the sole frontend, owning features end-to-end, architecture, UI
implementation, integration with APIs, validation and error handling. I care about clean, reusable UI
patterns (forms, tables, filters), monitoring real user behaviour (Sentry, performance optimizations) and
turning business requirements into interfaces that are fast, understandable and ready to evolve with the
product.

SKILLS
Languages: JavaScript, TypeScript, HTML5, CSS3, SCSS, JSON, Markdown

Frontend: React, React Router, Redux, React Query, Formik, Next.js, Tailwind CSS, Bootstrap, Material UI, Styled
Components, Vue.js, Vuex, Vue Router, Vuetify, Alpine.js, jQuery, Highcharts, Chart.js, React Native, Expo, Apache
Cordova

Backend: Node.js, Express.js, Nest.js, REST API, WebSockets, OpenAPI, OAuth 2.0, JWT

Databases: MongoDB

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, CI/CD, MVC/MVVM, Microservices Architecture, Performance Optimization, Clean Code & Refactoring

WORK EXPERIENCE
Front-End Developer | Drum’n’code 08.2021 - Present

Project #4: Furnishing Platform

Built a Chrome extension that lets users pin furniture from any site in 2 clicks, auto-filling price, title and image;
this reduced time to add a product to the platform by 63.4% and increased saved items per active user by 27.9%.

Implemented Sentry alerts with video replay for critical UI flows, decreasing average time-to-detect frontend
issues by 41.6% and cutting user-reported bug tickets by 18.3%.

Reworked all search sections from classic pagination to infinite scroll with responsive columns, increasing viewed
items per session by 22.7% without degrading Core Web Vitals.

Optimized list rendering and image loading within the new layout, reducing scroll jank and lowering layout shift
incidents by 31.2% on catalog pages.

Technologies: React, Redux, Material UI, Sentry

Project #3: Constructions Dashboar d

Implemented complex search UX (autocomplete + nested category tree + map sync), reducing time to find a
relevant construction project from 4-5 minutes to 1.6 minutes on average.

Built an authentication & subscription layer that hides premium data for non-paying users, increasing conversion
5
to paid access by 1 .4% while keeping performance stable.

Added virtualized scrolling for search results and map-related lists, cutting memory usage by 49.8% and reducing
long-task occurrences on heavy queries by 36.9%.

5
Tuned Leaflet map rendering and search linkage, decreasing map interaction latency by 28. % and improving
user satisfaction scores in internal feedback.

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Technologies: React, TypeScript, Tailwind CSS, Mob , Leafle t

Project #2: Payment System (Cards + Crypto)

Designed the front-end architecture and implemented two dashboards (for merchants and internal operators),
reducing time to add new reporting or settings pages by 33.1% thanks to reusable layout and form patterns.

Implemented OpenID-based authentication and fine-grained user management (store/wallet/action level), reducing
unauthorized access incidents to 0 and cutting support requests about “wrong access level” by 24.7%.

Built withdrawal and balance management flows with granular permissions (including “hide balances”), lowering
operational mistakes in financial actions by 19.3% and improving audit clarity for the support team.

Added browser-language-based internationalization and validation with React Hook Form, increasing completion
rate of onboarding flows by 14.6% for non-English users and reducing form submission errors by 21.8%.

Technologies: React, TypeScript, Tailwind CSS, OpenID, AG Grid, Sentry, i18n, Axios, React Hook Form

Project #1: US Wedding Agency Platform

Implemented a new UI layer based on shadcn components and Tailwind, improving design consistency across
booking flows and increasing overall UI reuse by 37.2%.

Developed a multi-step booking forms listing and submission flow, reducing time to complete a service booking
from 6.2 minutes to 3.9 minutes on average.

Integrated Zod-based validation into booking forms, lowering invalid submission rate by 23.5% and cutting back-
and-forth with support for incorrect requests.

Optimized Next.js pages for performance (code splitting, proper image usage), lifting Lighthouse performance
score on key booking pages from 81 to 94 and slightly increasing completion rate for mobile users by 9.8%.

Technologies: React, Redux Toolkit, TypeScript, Next.js, Tailwind CSS, shadcn/ui, Zod

EDUCATION LANGUAGES
Ukrainian State University

English Upper-Intermediate (В2)

Science and Technologies