Joosep Jääger
Software Engineer at Freelance
Tartu, Estonia
Summary
🤩
Rockstar🎓
Top SchoolJoosep Jääger is a software engineer based in Tartu, Estonia with a decade of experience building robust back-end systems and research-grade cryptographic and blockchain software. Currently at Input Output (IOHK) and freelancing, he contributes to Cardano’s ledger implementation—working on UTxO logic and Babbage-era fixes—which highlights his expertise in Haskell and high-assurance code. His background includes research roles at Cybernetica applying multiparty computation and zero-knowledge protocols, where he designed domain-specific languages and wrote substantial Haskell code. Joosep also has academic experience as a teaching and research assistant in machine translation and advanced mathematics, underpinning a strong theoretical foundation. Comfortable moving between research and production, he brings a blend of formal methods, functional programming, and practical engineering to complex distributed systems. An understated strength is his habit of improving test suites and tooling, reducing long-term maintenance risks in critical crypto infrastructure.
11 years of coding experience
3 years of employment as a software developer
Tallinn School No. 21Computer Programming, Computer Programming at Tallinn Secondary School of ScienceComputer Science, Computer Science at University of TorontoBachelor's degree, Computer Science, Bachelor's degree, Computer Science at University of Tartu
English, Estonian, Russian, German
Github Skills (6)
ledger10
cardano10
haskell10
blockchain10
implement10
testing9
Programming languages (17)
Github contributions (5)
IntersectMBO/cardano-ledger
Apr 2022 - Jan 2023
The ledger implementation and specifications of the Cardano blockchain.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:757 reviews, 107 commits, 251 PRs in 9 months
Contributions summary:Joosep primarily contributed to the core ledger implementation of the Cardano blockchain. They applied and integrated the `allOuts` function within the `Utxo.hs` and `Utxow.hs` modules, which involved code modifications in the Babbage era implementation. Additionally, the user addressed and corrected various test cases within the Babbage era, including adding necessary witnesses for reference scripts and fixing errors within the Tx generator. Further contributions include general formatting and code improvements.
blockchaincardanocryptocurrencyada
Soupstraw/fractalvr
Mar 2018 - Jul 2020
Contributions:2 releases, 2 PRs, 32 pushes in 2 years 4 months
virtual-realityrendererunityfractalreal-time
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