Marcin Kozak

Senior Full-Stack Engineer / Developer

[email protected]|Poland|linkedin.com/in/marcin-kozak-18919480

Professional Summary

Programming is my craft and my pleasure rolled into one. What I find most rewarding is discovering elegant solutions - ones that are optimal, clean, easily testable, and intuitive for any developer who looks at the code. Before I write a single line, I make sure I understand the business intent - only when I have the full picture of what and why we're building can I design something that truly works.

AI: I use opencode with cost-effective language models for prototyping, code exploration, debugging, and TDD test generation. AI handles routine tasks while I focus on architecture and quality.

Experience

Senior Full-Stack Developer

@ Polcar PPH2018 - Present

Lead architect and developer of Polcar's first web-based B2B e-commerce platform (automotive parts), serving a catalog of 100,000+ products and handling ~40% of company revenue. The platform (catalog.polcar.com) replaces a previously desktop-only solution — migration in progress. Development and maintenance of smaller landing pages for in-house brands.

Lead architect and developer of the B2B e-commerce platform — the company's first web application
Launched platform handling 100,000+ product catalog and ~40% of company revenue, migrating from desktop to web
Optimized data delivery from complex, heavy source databases — caching layer, query optimization, DB structure for read performance
Data integration from internal systems, normalization and data cleaning
Image delivery optimization with protection against unauthorized duplication
Internal CLI tool in .NET/C# for MS SQL to MySQL migration with schema transformation
Translation repository management system and language file tooling

Senior PHP Developer

@ ModulesGarden2014 - 2018

Developed ecosystem modules for the WHMCS hosting management platform. Worked on custom solutions including an internal project management tool, e-commerce integrations (Magento 1 cart, Magento 2 payment gateway), and a new system serving as a WHMCS alternative. Contributed to the official modulesgarden.com company website backend.

WHMCS module development and alternative WHMCS system
E-commerce integrations (Magento 1 cart, Magento 2 payment gateway)
Internal project management tool
Backend of modulesgarden.com company site

Frontend Developer (Freelancer)

@ Self-employed2005 - 2014

Built websites from design mockups using HTML, CSS, and JavaScript. Collaborated with interactive agencies and direct clients.

Delivered 30+ websites and landing pages
Collaborated with advertising agencies
Managed projects and budgets independently

Skills

Frontend

Vue.js 3 · Composition API, Pinia, TypeScript, JavaScript (ES6+), HTML5 / CSS3, Vite, Fetch API / Axios, Browser APIs, Quasar Framework 2, Nuxt.js, Tailwind CSS

Backend

Node.js, PHP, Laravel, C# / .NET, REST API

Databases

MySQL / MariaDB, MS SQL, Redis

DevOps & Tools

Docker / Docker Compose, Git, CI/CD, Linux (Nginx/Apache)

Testing

Vitest, PHPUnit, Playwright

Communication

WebSockets, Message Queues (RabbitMQ)

Education

Uniwersytet Pedagogiczny im. KEN w Krakowie

2007 - 2011

Licencjat — Informatyka

Languages

Angielski — B2

Projects

B2B/B2C E-commerce Platform

Lead frontend & API architect

PHP, Laravel, Vue.js, TypeScript, MySQL, Redis, Docker, C#, .NET

Lead architect and developer of the B2B/B2C e-commerce platform with an online product catalog (catalog.polcar.com). Responsible for optimizing data delivery from complex, heavy source databases and translating business requirements into performant web application solutions.

Lead architect and developer of the platform
Caching layer and query optimization for hundreds of thousands of products
Data integration from internal systems, normalization and cleaning
Image delivery optimization with duplication protection

Database Migration CLI (.NET)

Architect & Developer

C#, .NET, MySQL, MS SQL

Internal terminal tool for migrating data between MS SQL and MySQL with automatic type and schema transformation, including table merging while maintaining referential integrity.

Migrated 100+ tables with type and schema transformation
Reduced migration time from days to hours
Custom logic for table relationship transformation

Multi-language Management System

Full-Stack Developer

.NET, C#, MSSQL

Internal tool for managing translation repositories. Enables working with language files across multiple projects, automatic detection of missing translations, and data export into project structures.

Interface for managing multiple languages simultaneously
Automatic detection of missing translations
Export/import to project formats

ModulesGarden - Company Website

Backend Developer

PHP, Laravel

Co-developed the backend of the official company website modulesgarden.com. Implemented business logic and integrated with internal systems.

Backend of the modulesgarden.com company site
Integration with internal company systems
Business logic implementation