Daniel Hahn
Software Developer CTO at betterplace.org
Berlin, Germany
Summary
👤
Senior🎓
Top SchoolDaniel Hahn is a seasoned software developer and technical leader with nearly two decades of experience, currently serving as CTO at betterplace.org in Berlin. He combines full-stack expertise—spanning Rails-backed services, Elasticsearch extensions, and UI integrations—with hands-on contributions to open-source projects like chewy and team_dashboard. Known for improving search scoring and integrating diverse data sources, he pairs pragmatic engineering with product-oriented thinking. His career began in systems and UI work in C++/C# and evolved into team leadership and architecture for digital library and nonprofit platforms. Daniel often bridges backend complexity and frontend usability, for example implementing custom scoring in Elasticsearch and refactoring integrations across services. He holds a Diplom in Computer Science from KIT and brings a long track record of shipping robust, maintainable systems.
19 years of coding experience
10 years of employment as a software developer
Diplom, Computer Science, Diplom, Computer Science at Karlsruhe Institute of Technology (KIT)
Stackoverflow
3,772reputation
351kreached
63answers
3questions
ruby
top-5%
ruby-on-rails
top-5%
protected
top-5%
visibility
top-5%
Github Skills (32)
javascript10
scripting10
amazon-elasticsearch10
ruby10
elasticsearch-client10
elasticsearchquery10
aws-elasticsearch10
elasticsearch10
elasticsearch-api10
visibility9
protected9
apidoc9
angularjs9
api9
ruby-on-rails9
Programming languages (9)
Github contributions (5)
toptal/chewy
Jun 2014 - Feb 2017
High-level Elasticsearch Ruby framework based on the official elasticsearch-ruby client
Role in this project:
Back-end Developer
Back-end DeveloperContributions:14 commits, 3 PRs, 14 comments in 2 years 9 months
Contributions summary:Daniel primarily contributed to the `chewy` framework by implementing and extending the scoring functionalities within the Elasticsearch Ruby framework. The contributions include adding features like `script_score`, `boost_factor`, `random_score`, and `field_value_factor` to enable custom scoring and boosting within search queries. The user also added the ability to configure boost and score modes and refactored the code to add new functionality. Several code changes included updates to the core query criteria and specifications.
ruby-frameworkelastichigh-levelruby-clientruby
fdietz/team_dashboard
Apr 2013 - Dec 2013
Visualize your team's metrics all in one place.
Role in this project:Full-stack Developer
Full-stack DeveloperContributions:8 commits, 3 PRs in 8 months
Contributions summary:Daniel contributed significantly to the project by implementing new features and improving existing ones, primarily focused on integrating data sources and enhancing the user interface. They added a Jenkins game plugin, refactored existing Pingdom integrations, and implemented a new settings system. They also addressed bugs in the meter widget and the number widget, showing work across both frontend and backend aspects.
placereactall-in-onevisualizemetrics
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