Sebastian Hengst
Staff Software Engineer at Mozilla
Germany
Summary
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RockstarSebastian Hengst is a Staff Software Engineer in Germany with 17 years of experience building and stabilizing large-scale developer tooling and browser infrastructure. He leads a 15-person "code sheriffs" team at Mozilla, triaging CI failures, analyzing crash reports, and deciding fixes or rollbacks for Firefox releases. Hands-on across the stack, he contributes to Treeherder (Django/Python/React) automation, Taskcluster integrations, and query-driven reporting using BigQuery and MySQL to measure both quantitative and qualitative KPIs. His open-source work spans front-end UX fixes in Gaia and deep engine-level patches in gecko-dev, showing fluency from HTML/JS UI details to browser internals. Sebastian pairs operational rigor—emulating release builds and patching branches—with a pragmatic focus on automation that prevents regressions at scale. Colleagues rely on him not only for technical fixes but for designing the monitoring and processes that keep Firefox shipping reliably.
17 years of coding experience
German, English, French
Github Skills (20)
javascript10
c-language10
user-interface10
graphical-user-interface10
human-interface10
localization10
html10
cprogramming-language10
react10
debug9
networking9
ui-design9
front-end-development9
dom9
uid9
Programming languages (20)
Github contributions (5)
mozilla/gecko-dev
Mar 2014 - Jan 2023
Read-only Git mirror of the Mercurial gecko repositories at https://hg.mozilla.org. How to contribute: https://firefox-source-docs.mozilla.org/contributing/contribution_quickref.html
Role in this project:
Back-end Developer
Back-end DeveloperContributions:5581 commits in 8 years 11 months
Contributions summary:Sebastian primarily addressed issues related to the Firefox browser's core functionality, specifically focusing on session history, window creation, and content security policies. The commits involved substantial modifications to document loading, network utilities, and internal browser components, indicating a deep understanding of the browser's internal architecture. The user’s contributions suggest involvement in bug fixes and potentially performance optimizations within the browser engine.
repositoriesfirefoxmercurialgit-mirrormozilla
mozilla/treeherder
Apr 2015 - Jan 2023
A system for managing CI data for Mozilla projects
Role in this project:Full-stack Developer
Full-stack DeveloperContributions:349 reviews, 120 commits, 673 PRs in 7 years 10 months
Contributions summary:Sebastian primarily contributed to the front-end components and UI aspects of the Treeherder project, implementing features such as improved filter functionality and fixing bugs in the bug filer. Their work involved modifying React components, including the PushHeader and BugFiler components, to enhance user experience. Furthermore, the user updated the platform mappings and incorporated new platform names, demonstrating an understanding of the project's build environment and associated data structures.
reactpythondjango-rest-frameworkdjangodocker
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