Maciej Kozik, Developer in Wrocław, Poland
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Maciej Kozik

Verified Expert  in Engineering

Full-stack Web Developer

Wrocław, Poland
Toptal Member Since
August 26, 2020

Maciej is a full-stack web developer with hands-on experience in a range of technologies for the back end (Scala, Python) and front end (React, Redux) as well as databases (MySQL). Maciej loves building products that solve problems with style—without sacrificing usability. Besides Maciej's love for code, he enjoys providing guidance and planning tasks to complete project goals. This kind of work gives a different sense of fulfillment when you can view the growth of your team.


Redux, TypeScript, Amazon Web Services (AWS), Python, SQL, Auth0, Kubernetes...
Redux, TypeScript, Python, Distributed Systems, Java, Kubernetes, Docker, gRPC...
Python, SQL, Ember.js, Docker, MariaDB




Preferred Environment

MacOS, Slack, Arch Linux, OS X

The most amazing...

...experience I've had was working on a highly distributed, scalable chatbot platform, with a tightly knit team.

Work Experience

Full-stack Developer

2019 - PRESENT
  • Planned and executed the transition from multiple repositories to a mono repository along with implementing the switch to GitHub Actions for the CI.
  • Took ownership of the internal admin tool and helped to improve code quality by restructuring it to hexagonal architecture.
  • Evangelized extracting logic into microservices when the domains were clearly separable.
  • Planned and engineered migration to Auth0 to delegate authentication to a third party, improving security and unifying account management across the platform.
  • Optimized and refactored an established React app which reduced the number of redundant re-renders and data fetches.
Technologies: Redux, TypeScript, Amazon Web Services (AWS), Python, SQL, Auth0, Kubernetes, Docker, Terraform, PostgreSQL, React, Scala

Full-stack Developer

2018 - 2019
  • Implemented front-end customer messaging and administration platform using React, Redux, and GraphQL.
  • Performed data migrations and architected analytic events aggregation in a non-relational database (MongoDB).
  • Designed and wrote Python-based microservices serving machine learning models, with gRPC for communication.
  • Participated in planning the product roadmap, task preparation, and distribution among the developers.
Technologies: Redux, TypeScript, Python, Distributed Systems, Java, Kubernetes, Docker, gRPC, GraphQL, MongoDB, React, Scala


2017 - 2018
  • Created several fault-tolerant microservices that were orchestrated via Celery.
  • Designed and implemented a RESTful API that also adhered to the JSON API.
  • Performed relational schema migrations with Alembic.
  • Implemented semi-supervised keyword extraction from websites.
  • Wrote the whole front-end app in Ember.js, including custom data visualizations with D3.js.
Technologies: Python, SQL, Ember.js, Docker, MariaDB

I developed an open-source module for Python that allows you to run SQL queries against XML documents. The idea was born when I was trying to work with StackExchange data dumps that were unsuitable for keeping in memory whole while simultaneously was also to slow to iterate over with the ElementTree XML API.
2019 - 2020

Master's Degree in Computer Science

Politechnika Wrocławska - Wrocław, Poland

2016 - 2019

Bachelor's Degree in Computer Science

Politechnika Wrocławska - Wrocław, Poland


React, Node.js


Auth0, Terraform


Redux, gRPC, Ember.js


Docker, Kubernetes, Amazon Web Services (AWS), Arch Linux, MacOS


Scala, GraphQL, Python, SQL, TypeScript, Java, Go


MongoDB, PostgreSQL, MariaDB


Distributed Systems

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