Johannes Müller
Team Lead at Crystal Programming Language
Fulda, Hesse, Germany
Summary
🤩
Rockstar🎓
Top SchoolJohannes Müller is a seasoned software leader with 13 years of experience, currently serving as Team Lead and core contributor to the Crystal programming language. He blends deep systems and back-end expertise with full-stack documentation and tooling work, having improved the Crystal compiler, docs generator, and the Shards dependency manager. As Principal Engineer at Manas.Tech and an active open-source maintainer since 2018, he balances hands-on coding, performance-minded refactors, and community coordination. He also runs freelance web/devops work and event technology projects, reflecting a practical, multidisciplinary approach. Based in Fulda, Germany, Johannes is notable for shipping user-facing documentation features (live code runners and playground fixes) alongside low-level interpreter and path-resolver bug fixes—demonstrating both product sensitivity and developer-tooling rigor.
13 years of coding experience
2 years of employment as a software developer
Bachelor of Science (B.Sc.), Angewandte Informatik, Bachelor of Science (B.Sc.), Angewandte Informatik at Fachhochschule FuldaAngewandte Informatik, Angewandte Informatik at Otto-Friedrich-Universität Bamberg
German, English, Spanish, Latin
Stackoverflow
5,611reputation
75kreached
135answers
3questions
Github Skills (24)
dependency-management10
crystal-lang10
testing10
css10
command-line-interface10
interpreter10
command-line10
html10
documentation10
cli10
javascript9
yaml9
parsing9
refactoring8
regular-expression8
Programming languages (24)
Github contributions (5)
crystal-lang/shards
Jun 2018 - Jan 2023
Dependency manager for the Crystal language
Role in this project:
Back-end Developer
Back-end DeveloperContributions:8 releases, 145 reviews, 59 commits in 4 years 8 months
Contributions summary:Johannes primarily contributed to the development and maintenance of the dependency manager's core functionalities, focusing on improving the path resolver and fixing related bugs. They implemented several tests to ensure the correct behavior of the path resolver. Furthermore, the user extended the documentation and improved the user interface and help messages of the CLI tool. They also refactored the code for better dependency management.
dependency-managercrystal-languagecrystal
crystal-lang/crystal-book
May 2017 - Jan 2023
Crystal reference with language specification, manuals and learning materials
Role in this project:Full-stack Developer
Full-stack DeveloperContributions:338 reviews, 106 commits, 373 PRs in 5 years 8 months
Contributions summary:Johannes contributed to the Crystal book by modifying the project's styling, adding code sample runners using CarcinPlay, and introducing a landing page. They fixed the error display in the playground, and updated the Crystal version. The user's work involved both front-end and back-end modifications, enhancing the user experience and functionality of the documentation.
logic-programmingcrystal-langcrystallanguage-designlang
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