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Available for senior frontend roles

Dmytro Kosianchuk

Frontend Engineer crafting fintech & enterprise interfaces in React, TypeScript & Next.js.

5+ years shipping real payment flows, dashboards and accessible UIs — engineered for speed, clarity, and the next teammate who reads the code.

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Location
Kyiv · Remote
Stack
React · Next · TS
Experience
5+ years
Response
< 24h
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Selected work

Things I've shipped

Checkbox2024 — 2025

DubiDoc — E-Document Signing Platform

Frontend Developer · Checkbox.ua

Impact First B2B SaaS at Checkbox · Multi-party e-signatures · Launched 2024

ReactNext.jsTypeScriptTanStack Query
Read the case study

Problem

Ukrainian businesses were drowning in paper. They needed a secure B2B platform to create, route, and legally sign documents in one place — with multi-party approval chains, strict audit trails, and zero room for trust failures.

What I did

Owned the full document lifecycle UI: drag-and-drop signing order builder, real-time participant status timeline, inline PDF viewer with annotation support. Designed defensive UX for every edge case — expired signatures, network drops, declined approvals. Built reusable form components shared across the product suite.

Result

Shipped the entire signing journey on schedule. Became Checkbox's first standalone B2B SaaS product, opening a new market segment and positioning the company in Ukraine's digital compliance space.

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Checkbox2023 — 2024

Checkbox PRRO — Fiscal Cash Register

Frontend Developer · Checkbox.ua

Impact Thousands of active locations · 0 critical fiscal errors · Flagship revenue product

ReactTypeScriptWebSocketREST API
Read the case study

Problem

Ukraine legally mandated software fiscal registers for all retailers. Businesses needed a cashier UI so fast and reliable that it could survive slow connections and handle hundreds of transactions per shift — with absolutely zero tolerance for fiscal data errors.

What I did

Built the cashier-facing interface: receipt creation, returns, and shift management. Implemented optimistic UI so interactions felt instant regardless of connection speed. Handled complex multi-rate tax logic and deeply integrated with the State Tax Service (DPS) API. Covered all transaction edge cases with bulletproof error handling.

Result

Rolled out to thousands of business locations across Ukraine. Zero critical fiscal data transmission failures post-launch. PRRO became the flagship Checkbox product and the company's primary recurring revenue source.

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EPAM2022 — 2023

Avid MediaCentral — Newsroom Platform

Frontend Developer · EPAM Systems

Impact WCAG 2.1 AA on first review · 20+ typed components · Broadcast clients worldwide

ReactTypeScriptWCAG 2.1i18n
Read the case study

Problem

Broadcast newsrooms worldwide needed a modern web interface for real-time multi-source media monitoring. The existing solution was slow, visually inconsistent, and failed WCAG accessibility requirements — blocking adoption in regulated markets.

What I did

Developed the live monitoring dashboard: real-time aggregated news feed, multi-source filtering, inline editable data grid. Led all accessibility work — semantic HTML, ARIA patterns, full keyboard navigation — until the platform passed a WCAG 2.1 AA audit. Built a 20+ component TypeScript library shared across 3 product teams.

Result

Platform shipped on time and deployed to broadcast newsrooms globally. WCAG 2.1 AA audit passed on the first review — no rework cycle. Shared component library reduced duplicate implementation effort by an estimated 60% across teams.

EPAM2021 — 2022

Retail Platform — E-commerce Redesign

Frontend Developer · EPAM Systems

Impact Core Web Vitals improved · 5 locales · SPA migration on schedule

ReactTypeScriptSCSSi18nWebpack
Read the case study

Problem

A major European retailer's e-commerce platform had accumulated years of tech debt: inconsistent UI across markets, broken accessibility, and performance bottlenecks that were directly contributing to cart abandonment at checkout.

What I did

Led the full front-end overhaul. Migrated core pages from a legacy template-based system to a structured React SPA. Built a new component library with strict TypeScript, implemented i18n across 5 locales, and overhauled the asset delivery pipeline — lazy loading, code splitting, modern image formats — targeting measurable Core Web Vitals gains.

Result

Core Web Vitals improved across all key conversion pages. Unified design system shipped consistently across 5 locales. New architecture reduced new feature delivery time dramatically — teams could ship in days what previously took weeks.

Achievements

Measurable impact

85%

Performance boost

LCP 4.2s → 1.8s on checkout: code-splitting, lazy routes, lean validation.

80%

Bug reduction

Transaction state machine (WebSocket + fallback) — stuck-payment tickets ↓80%.

20+

Component library

Typed React kit: 20+ components up to PDF signatures — full TypeScript.

60%

Codebase migrated

Class components → Hooks + Zustand; TypeScript coverage 40% → 85%.

Tech stack

Technologies I work with

01

Frontend Core

React 18Next.jsTypeScriptApp RouterHTML5SCSS
02

State & Tools

ZustandTanStack QueryTailwind CSSViteWebpackJest
03

Craft & Quality

SSR/SSG/ISRWebGLGSAPA11yi18nPerformance
Career Path

Work Experience

2023 — Feb 2026Fintech

Frontend Developer

Checkbox.ua

  • Fintech SPAs (React, Next.js, TS): payments, admin, internal tools
  • Complex forms, transactions, defensive UI for sensitive flows
  • Core Web Vitals: checkout page LCP 4.2s → 1.8s
  • Shared components for checkout & dashboards; close work with backend/QA
React 18Next.jsTypeScriptTanStack QueryWebSocket
2021 — 2023Enterprise

Frontend Developer

EPAM Systems

  • Enterprise SPAs for international clients (retail, media)
  • Accessibility (WCAG 2.1 AA), i18n, strict TS standards
  • Component library with 20+ typed components and full docs
  • Comprehensive test coverage: unit, integration, E2E
ReactTypeScriptSCSSJestRTL
2019 — 2021Freelance

Layout Developer

Freelance

  • Semantic HTML/CSS, responsive marketing and small-business sites
  • JS for UI, validation, simple backend hooks
  • Implementation from handoffs and client feedback
HTMLCSSJavaScriptResponsive
About Me

Pixel-level UI, production-grade engineering

Kyiv · remote-friendly. I build React / Next.js SPAs for payments, documents and internal tools — profiling before spinners, strict TypeScript, and code written for the next teammate, not just the demo.

I care about the boring parts that users feel: a checkout that stays responsive on a train, a form that never loses your input, an interface a screen reader can actually navigate. The flashy stuff is just proof the fundamentals are solid.

0+Years Experience
0+Projects Delivered
0Companies
Dmytro Kosianchuk
Kyiv · Remote · 2026
Get in Touch

Let's build something great

Open to senior frontend roles and freelance projects. I respond within 24 hours.

Message on Telegram
Emailkosianchuk.d@gmail.comPhone+380 99 771 64 73GitHub/kosianchuk

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Designed & Built by Dmytro Kosianchuk

Built with care · WebGL · GSAP