Hello, I'm

Kostyantin Slabenko

aka Konstantin Kai

Senior Software Engineer & Frontend Team Lead

13+ years building high-traffic B2C apps. Lead the frontend team, design architecture, ship open-source. Use Claude Code daily. Odesa, Ukraine.

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About

Building the web for over a decade

Frontend Team Lead, 13+ years on high-traffic B2C apps. Ran a team of 10. Cut build times 35% and release cycles 50% through architecture work. Daily stack: React, TypeScript, React Native, Flutter.


Wrote native mobile modules in Objective-C and Java to fix memory crashes the JS layer couldn't handle. Mentor engineers, review code, ship open-source. Build solo projects in full vibe-coding flow with Claude Code.


Finished Master's in Software Engineering. Thesis: predicting developer productivity from TypeScript code analysis with ML.

Experience

Where I've worked

2020 — Present

Frontend Team Lead

Centro — Creator economy SaaS platform

  • Led a team of up to 10 engineers with 1-on-1s, performance reviews, and roadmap planning
  • Hired and onboarded 5 engineers through technical interviews
  • Reduced build times by 35% through Nx monorepo adoption
  • Cut release cycles by 50% with CI/CD pipeline automation
  • Designed, built, and shipped BigWish.com in collaboration with Claude Code
  • Wrote Frontend Developer Contract: guidelines for engineers shipping with AI agents

2018 — 2020

Senior Frontend Engineer

Centro

  • Redesigned core product with feature-based architecture
  • Developed hybrid SSR/CSR rendering solution
  • Built TikTok-inspired media player with virtualized lists

2016 — 2018

Flutter Mobile Engineer

Centro

  • Led cross-platform mobile development for Android and iOS
  • Published open-source Uploadcare library (328+ downloads)

2015 — 2016

React Native Engineer

Centro

  • Wrote TypeScript typings for Expo (@types/expo). Expo team adopted them as the basis for official types
  • Built native file upload modules in Objective-C & Java, solving memory crashes

2013 — 2015

Frontend Engineer

Centro

  • Migrated PHP-based builds to Webpack
  • Implemented real-time video streaming via WebRTC
  • Introduced TypeScript to the organization

2012 — 2013

Earlier Career

PRCode, UATrade

  • Full-stack PHP development, database design
  • Web development with Drupal, Joomla, Bitrix

Skills

Technologies I work with

Languages

TypeScript JavaScript Dart Rust Java Objective-C

Frontend

React Next.js Tailwind CSS Vite Webpack WebRTC

Mobile

React Native Flutter Expo

Infrastructure

Nx CI/CD Git Firebase

AI-Assisted Development

Vibe Coding Claude Code Opencode

Testing

Vitest Jest Testing Library

Open Source & Projects

Things I've built

ReelKit ↗

Single-item virtualized slider for TikTok/Instagram Reels-style experiences. Touch-first, zero dependencies. Supports React, Angular, and Vue.

TypeScript React Angular Vue GitHub ↗

Uploadcare Flutter ↗

Open-source library for file uploading via Uploadcare. Published on pub.dev with 328+ downloads.

Dart Flutter pub.dev

PeekAPI ↗

Plug-in analytics platform for REST APIs. Real-time dashboard with request metadata, charts, and alerts. SDKs for Node, Python, Go, Ruby, PHP, Java, Rust, and Dart.

Next.js TypeScript Multi-language SDKs

BigWish.com ↗

Wishlist and gifting platform. Built from scratch in collaboration with Claude Code.

Next.js TypeScript React Claude Code

Frontend Developer Contract

Guidelines and conventions for engineers shipping code alongside AI coding agents. My team uses it to keep PRs reviewable.

Documentation AI Agents Best Practices

Proto Dart/Flutter Plugins

Rust plugins adding Flutter and Dart toolchain support to moonrepo/proto version manager.

Rust Proto Flutter Plugin ↗ Dart Plugin ↗

Proto PHP/Composer Plugins

Rust WASM plugins for managing PHP and Composer versions via moonrepo/proto version manager.

Rust WASM Proto PHP Plugin ↗ Composer Plugin ↗

@types/expo

TypeScript typings for Expo SDK that became the foundation for Expo's official TypeScript support. Received recognition from Expo team.

TypeScript Expo React Native

Triton Events ↗

Frontend for a triathlon, running, and swimming events platform based in Odesa, Ukraine.

React MobX

StandForUkraine.com ↗

Humanitarian initiative supporting Ukraine. Contributed to development.

React Open Source

Contact

Let's work together

Open to new opportunities. Drop a line.

[email protected] GitHub LinkedIn Blog