Jan Koziński
Full Stack React Ruby On Rails Developer at TheWidlarzGroup - React Native Consultants
Lower Silesian Voivodeship, Poland
Summary
🤩
Rockstar🎓
Top SchoolJan Koziński is a Full Stack React and Ruby on Rails developer with 5 years of experience building web and mobile products that scale, including work on large MySQL and MongoDB datasets (1B+ records / 100M+ documents). He combines hands-on implementation—React Native front-ends, REST APIs, microservices enthusiasm—and backend optimisation with disciplined TDD (RSpec) to deliver maintainable, business-aligned software. At TheWidlarzGroup he led GPT fine-tuning and LLM integration, migrated data models and repos, and reduced query time and costs while collaborating across US timezones. A contributor to open source, he also builds demonstrative mock backends and uses analytics tooling like New Relic to track elusive bugs, showing a practical focus on observability as much as features. Based in Lower Silesia, Poland, he’s completing graduate studies in computer science and prefers long-term, testable solutions that bridge product needs and engineering hygiene.
4 years of coding experience
Master's Degree, Computer Science, Master's Degree, Computer Science at Wrocław University of Science and TechnologyBachelor of Engineering - BE, Information and Communication Technology, Bachelor of Engineering - BE, Information and Communication Technology at Wroclaw University of Science and Technology
Polish, English, Spanish
Github Skills (23)
ios10
react-native10
emoji10
mapview10
android10
google-maps10
maps10
react10
kml9
toast9
notification9
typescript8
geojson8
sdk7
notification-center6
Programming languages (6)
Github contributions (5)
jan-kozinski/mikroblog-v2
Aug 2021 - Jan 2024
Contributions:5 PRs, 74 pushes, 12 branches in 2 years 5 months
TheWidlarzGroup/holidaily
Mar 2022 - Jan 2023
🌴☀️🌴☀️🌴
Contributions:35 reviews, 539 commits, 5 PRs in 10 months
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