Konstantin Haase
Berlin, Germany
Summary
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Rockstar🎓
Top School
Top expert inRuby Web Development and E-commerce Technologies
Konstantin Haase is a seasoned software developer and entrepreneur based in Berlin with 17 years of hands-on experience across full-stack, backend, and DevOps roles. He has contributed to prominent open-source Ruby projects and CI tooling—most notably Travis CI, Sinatra, Rack, Puma, and Rubinius—working on everything from core language internals and web server behavior to API design, deployment tooling, and frontend clients. Konstantin pairs pragmatic engineering with strong documentation skills, repeatedly improving READMEs, docs, and developer UX alongside feature work. He blends systems-level thinking (JIT, ObjectSpace, HTTP semantics) with practical delivery (build scripts, deployment strategies, CORS, and CLI tools), and his background in IT-Systems Engineering underpins a disciplined approach to reliability and performance. An understated strength is his ability to move between deep backend plumbing and polished frontend/devops improvements, making him effective in cross-disciplinary engineering teams.
17 years of coding experience
Abitur, Abitur at Georg-Cantor-GymnasiumB.Sc., IT-Systems Engineering, B.Sc., IT-Systems Engineering at Hasso Plattner InstituteStudenten, Marine Biology, Swedish, Studenten, Marine Biology, Swedish at Gullmarsgymnasiet
German, Latin, Norwegian, Swedish, English, German
Stackoverflow
25,803reputation
1.2mreached
111answers
1question
inheritance
top-5%
constants
top-5%
logging
top-5%
websocket
top-5%
sinatra
top-1%
ruby
top-1%
Github Skills (78)
testing10
http10
ruby10
emberjs10
heroku10
rack10
rest-api10
markdown10
javascript10
api10
front-end-development10
sh10
multiline10
compiler10
shell10
Programming languages (16)
Github contributions (5)
travis-ci/travis.rb
Jan 2013 - Dec 2017
Travis CI Client (CLI and Ruby library)
Role in this project:
Back-end & DevOps Engineer
Back-end & DevOps EngineerContributions:688 commits, 10 PRs, 22 pushes in 4 years 11 months
Contributions summary:Konstantin contributed to the development and maintenance of the Travis CI Client, focusing on backend logic and command-line interface (CLI) enhancements. Their work included fixing exceptions in command loading, implementing the `whoami` and `endpoint` commands, and adding support for environment variable handling. The user also implemented and maintained the infrastructure by adding configuration files and automating key management using shell scripting.
clirubytravis-ci
sinatra/sinatra
Apr 2010 - Jan 2016
Classy web-development dressed in a DSL (official / canonical repo)
Role in this project:Back-end Developer
Back-end DeveloperContributions:2 reviews, 915 commits, 6 PRs in 5 years 10 months
Contributions summary:Konstantin's commits primarily focus on modifying the Sinatra framework's core functionality. The contributions involve adding pattern matching to filters, refining error handling, and improving the handling of HTTP requests. They also address issues related to URL parameter handling, ensuring that the framework functions correctly with a variety of URL structures. Several commits also address template engine compatibility and ensure the application performs well with different template systems.
dslweb-developmentrubyrackweb-framework
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