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Mateusz Kowalski

@mateuszkowalski

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Senior Full Stack Engineer delivering scalable web apps, secure APIs, and LLM-powered products.

Poland

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What I'm looking for

I’m looking to build scalable, secure products in collaborative Agile teams—where I can lead architecture, improve performance, and ship AI/LLM capabilities in production. I want a place that values clean code, testing, and continuous learning.

I’m a Senior Full Stack Engineer with 9 years of experience delivering scalable web applications, high-performance backend systems, and AI-driven platforms across healthcare and fintech. I bring a broad, modern skillset—strong API development, microservices architecture, and cloud-native systems—focused on building solutions that are secure, maintainable, and fast.

In my most recent role, I architected and delivered end-to-end applications using React, Next.js, Vue, Nuxt, and Angular, while implementing robust backend services with Node.js (Express, NestJS) and Python (FastAPI, Django, Flask). I integrated LLM-powered chatbot capabilities into production, designed microservices-based distributed systems, and improved system performance and user experience—reducing load times by 35% and deployment efficiency by 40% through frontend optimization and backend enhancements.

I’m also experienced in building production-grade RESTful APIs and GraphQL services, optimizing databases (PostgreSQL, MongoDB, MySQL, Redis, Elasticsearch), and supporting reliability with TDD, automated testing, and CI/CD pipelines. I’m known for technical leadership—leading code reviews, mentoring, and collaborating closely in Agile/Scrum teams—to translate complex requirements into clean code, strong architecture, and data-driven outcomes.

Experience

Work history, roles, and key accomplishments

Senior Full Stack Engineer

Polcode

Apr 2021 - Mar 2026 (4 years 11 months)

Architected and delivered scalable web and backend systems, including AI-powered chatbot features using LLMs/NLP. Improved scalability by 40% and reduced load times by 35% through microservices architecture, API work, and frontend SSR/code-splitting.

React Next.js fastAPI Microservices GraphQL PostgreSQL Docker CI CD

Full Stack Engineer

Post Acute Analytics

Jan 2019 - Mar 2021 (2 years 2 months)

Built scalable full-stack applications with React/Vue and Python-based backend services for a multi-tenant platform serving thousands of users. Improved backend performance by 45% using database optimization and caching, and implemented secure REST APIs with JWT and OAuth 2.0.

React Vue.Js REST APIs OAuth 2.0 PostgreSQL MongoDB Redis

Software Engineer

STX Next

Jul 2017 - Dec 2018 (1 year 5 months)

Developed AI-driven web applications by integrating React frontends with Python backend services and high-throughput microservices. Partnered with data science teams to deploy and integrate machine learning models into production and modernized legacy systems into modular architectures.

React Python NLP REST APIs Microservices CI CD