Derk-jan Karrenbeld
Partner And Co-Founder at Delft Solutions
Rotterdam, South Holland, Netherlands
Summary
🤩
Rockstar🎓
Top SchoolDerk-jan Karrenbeld is a pragmatic technology founder and engineer with 13+ years building scalable web and mobile systems, currently co-leading Delft Solutions and freelancing through XP Bytes. He blends hands-on full‑stack work—from Android SDK fixes and React front-end improvements to TypeScript/JavaScript exercism tracks—with architecture, team leadership and product thinking honed as interim CTO and longtime technical lead. A committed open-source contributor (notably to react-static and exercism’s v3/javascript/TypeScript tracks), he cares deeply about accessibility, clean design and maintainable developer experiences. Comfortable with high‑throughput APIs, GDPR-compliant data practices and cross‑team coordination, he prefers bold, clever ideas over transactional incentives and mentors regularly through Exercism. An unusual signal of his pragmatic skepticism: he deliberately uses an emoji in his profile to detect automated recruiter outreach—proof he values intent and human communication.
13 years of coding experience
21 years of employment as a software developer
Gymnasium Diploma Nature Health and Science, Gymnasium Diploma Nature Health and Science at Gymnasium HaganumMinor Game and Interactive Media Design, Minor Game and Interactive Media Design at Utrecht UniversityBachelor of Science Computer Science, Bachelor of Science Computer Science at Delft University of Technology
English, Dutch, French, German
Stackoverflow
1,944reputation
137kreached
13answers
4questions
android
top-5%
android-view
top-5%
material-design
top-5%
Github Skills (50)
babel610
deeplink10
git10
javascript10
develop10
typed-array10
multidimensional-arrays10
jes10
testing10
arrayobject10
dynamic-array10
typescript10
android-sdk10
deep-linking10
java10
Programming languages (58)
Github contributions (5)
exercism/javascript
Jan 2019 - Dec 2022
Exercism exercises in JavaScript.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:454 reviews, 302 commits, 733 PRs in 3 years 11 months
Contributions summary:Derk-jan's contributions primarily involve refactoring and enhancing the JavaScript code within the exercism/javascript repository. They focused on migrating default exports to named exports in multiple exercises, including grade-school, linked-list, and robot-name. Additionally, they integrated several new exercises, like resistor-color and rna-transcription, while updating dependencies and upgrading the build environment to Babel 7.
javascriptexercismexercism-exercisesexercism-trackcommunity-contributions-paused
exercism/typescript
Apr 2019 - Oct 2022
Exercism exercises in TypeScript.
Role in this project:Back-end Developer
Back-end DeveloperContributions:195 reviews, 107 commits, 573 PRs in 3 years 7 months
Contributions summary:Derk-jan primarily contributed to syncing and updating exercise code for the TypeScript track. They synchronized exercise files related to `saddle-points` and `simple-cipher` to new versions, including related test updates and code modifications. Additionally, the user refactored the `matching-brackets` exercise, renaming it and modifying the test structure. The user also worked on other minor fixes.
typescriptexercismexercism-exercisesexercism-trackcommunity-contributions-paused
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