Stefan Kaes

Hamburg, Germany

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Summary

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Rockstar

🎓

Top School

Stefan Kaes is a seasoned systems architect and programming languages expert with 14+ years of professional software experience and a PhD in computer science. He’s known for deep expertise in language design and implementation, extensive OO framework design, and global recognition as a Ruby on Rails performance authority. At XING he led architecture efforts for over a decade and has consulted on compiler and large-scale middleware projects for enterprises like Siemens and Dresdner Bank. An active open-source contributor, Stefan has improved tooling across the Ruby ecosystem (ruby-prof, RVM) and contributed pragmatic fixes to notable projects including ZeroMQ bindings and Shopify’s krane. He combines a researcher’s rigor—type inference and compiler background from TU Darmstadt—with hands-on talent for performance tuning, testing, and cross-version compatibility. Based in Hamburg, he thrives on solving hard IT problems where correctness, speed and maintainability intersect.

14 years of coding experience

20 years of employment as a software developer

Technischen Universität Darmstadt

Github Skills (33)

debugging10

kubernetes10

debug10

zeromq10

netmq10

testing10

mq10

kubectl10

rvm10

c1110

data-structure10

ruby10

c1710

regular-expression10

profiling10

Programming languages (11)

JavaShellC++CMakefileJavaScriptGoHTML

Github contributions (5)

ruby-prof/ruby-prof

Feb 2013 - Jan 2020

A ruby profiler. See https://ruby-prof.github.io for more information.

Role in this project:

Back-end Developer

Contributions:210 commits, 31 PRs, 80 pushes in 7 years

Contributions summary:Stefan primarily contributed to improving the Ruby profiler, `ruby-prof`. Their work involved fixing bugs related to different Ruby versions (1.8.7) and measurement modes (GC_TIME, GC_RUNS, MEMORY, CPU_TIME), ensuring the tool's compatibility and accuracy. Furthermore, the user refactored code related to enabling/disabling GC stats and added fiber support. They also addressed issues related to printer output and test stability, along with general code cleanup and optimization.

railsruby

rvm/rvm

Oct 2012 - Dec 2022

Ruby enVironment Manager (RVM)

Role in this project:

Back-end Developer

Contributions:3 reviews, 72 commits, 54 PRs in 10 years 4 months

Contributions summary:Stefan primarily contributed to the RVM project by updating patches related to Ruby version management. Their work involved modifying code within various patch files, specifically targeting compatibility and functionality enhancements for older Ruby versions (1.8.7). The modifications appear to address specific issues, potentially focusing on GC (Garbage Collection) and RailsBench integration. These changes likely aimed at improving the stability and performance of Ruby environments managed by RVM.

ruby-environmentmri-rubyrbxrailsruby

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