Fabian Jahr
Open Source Contributor at Freelancer
Berlin, Germany
Summary
🤩
Rockstar🎓
Top SchoolFabian Jahr is an experienced back-end engineer and open source contributor based in Berlin with 11 years in software engineering and a track record of shipping production-grade blockchain infrastructure. He has contributed meaningful test automation, RPC fixes, wallet improvements and performance pieces to high-profile projects like Bitcoin Core, Bitcoin ABC (eCash) and Peercoin, demonstrating deep familiarity with node internals and cross-module code changes. As a self-employed consultant and interim CTO he blends hands-on C++/systems work with product and architectural leadership from founding a startup to advising clients. Supported by grants for open-source maintenance, he pairs rigorous QA practices with pragmatic bugfixes that improve reliability on platforms such as macOS — a detail that highlights his attention to platform-specific test stability. His academic background in finance and supply chain from WHU complements a systems-oriented mindset useful for consensus-critical software.
11 years of coding experience
6 years of employment as a software developer
Exchange Semester, Exchange Semester at Washington University in St. LouisB.Sc., Finance, Supply Chain Management, B.Sc., Finance, Supply Chain Management at WHU – Otto Beisheim School of Management
Stackoverflow
469reputation
17kreached
5answers
11questions
Github Skills (28)
crypto-wallet10
wallet10
c-language10
python10
bitcoin-wallet10
testing10
bitcoin10
bitcoins10
cryptocurrency10
rpc10
cplus10
blockchain10
litecoin10
cpp10
cprogramming-language10
Programming languages (18)
Github contributions (5)
bitcoin/bitcoin
Jul 2019 - Jun 2022
Bitcoin Core integration/staging tree
Role in this project:
Back-end Developer & QA Engineer / Test Automation Engineer
Back-end Developer & QA Engineer / Test Automation EngineerContributions:1092 reviews, 119 commits, 144 PRs in 2 years 11 months
Contributions summary:Fabian primarily contributed to test-related code, focusing on functional testing of the Bitcoin Core project. Their work included identifying and skipping flaky tests on macOS, adding tests for loading a serialized blockchain, fixing an RPC client timeout issue, and adding documentation for deactivating transaction fees. The user demonstrated a good understanding of the project's codebase by making changes that affected multiple modules and testing different scenarios. They also made various changes to the tests and added or extended some tests to cover new or existing functionality.
cryptographyp2pc-plus-pluscryptocurrencybitcoin-core
peercoin/peercoin
Jul 2019 - Jan 2022
Reference implementation of the Peercoin protocol.
Role in this project:Back-end Developer
Back-end DeveloperContributions:83 commits in 2 years 6 months
Contributions summary:Fabian focused on improving the Peercoin codebase through various updates, including fixing an RPC client timeout option and adding a test for the loadblock option. They also addressed a wallet issue related to resetting reused transaction caches to prevent incorrect trust levels. Furthermore, the user contributed to code refactoring efforts by extracting a GetBogoSize function and improved the gettxoutsetinfo RPC by adding a hash type. Their work also included enhancements to the avoid reuse functionality in wallet operations.
proof-of-stakeblockchaindecentralizedminablecryptocurrency
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