Juliusz Kościołek
Software Engineer IV at Software Mansion
Krakow, Lesser Poland Voivodeship
Summary
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Rockstar🎓
Top SchoolJuliusz Kościołek is a Software Engineer IV based in Krakow with 7 years of full‑stack experience, specializing in frontend systems built on JavaScript/TypeScript and React. He has driven large-scale refactors, CI and testing strategies, and performance and accessibility improvements for enterprise platforms at Guidewire and bespoke SaaS for pharmaceutical clients. At Guidewire he led design-system API work, micro-frontend productionization, complex release rollouts and tooling that automated migrations and analyzed module graphs. He contributes to prominent open-source projects such as react-native-reanimated, improving iOS layout animations and cross-platform stability. Comfortable across Next.js, Node and PostgreSQL, he combines pragmatic backend skills with deep React performance expertise and a focus on long-term maintainability. Outside core work he builds end-to-end products—from ETL and AWS pipelines to dashboards and bots—demonstrating hands-on ownership from infrastructure to UX.
7 years of coding experience
4 years of employment as a software developer
Bachelor of Engineering - BE Computer Science, Bachelor of Engineering - BE Computer Science at AGH University of Krakow
Github Skills (6)
mobile10
ios10
react-native10
animation10
javascript9
gesture9
Programming languages (3)
Github contributions (5)
software-mansion/react-native-reanimated
Oct 2022 - Jan 2023
React Native's Animated library reimplemented
Role in this project:
Mobile Developer (iOS)
Mobile Developer (iOS)Contributions:110 reviews, 45 commits, 35 PRs in 3 months
Contributions summary:Juliusz primarily contributed to the iOS implementation of the `react-native-reanimated` library, specifically focusing on layout animations. Their work involved fixing bugs related to the registration and management of exiting view ancestors and components being placed under the screen header on Android. The user addressed issues with the layout after entering animations and navigating during exiting animations. They also cleaned up and improved the layout animation code.
reactanimationanimatedreact-nativejavascript
software-mansion-labs/react-scan
Feb 2025 - Mar 2025
Scan for React performance issues and eliminate slow renders in your app
Contributions:2 releases, 2 PRs, 8 pushes in 19 days
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