Marcin Kostrzewa
Founder, CEO at Reilabs
Lisbon, Lisbon, Poland
Summary
🤩
Rockstar🎓
Top SchoolMarcin Kostrzewa is a founder and seasoned software leader with 14 years of experience building high-performance systems in compilers, cryptography, big data and language runtimes. As CEO of Reilabs and former Founder/CTO and language designer at Enso (formerly Luna), he led design and implementation of a purely functional language, its compiler, type checker and interpreter while exploring zero-cost interoperability and performant dynamic runtimes. He combines hands-on backend engineering—demonstrated by contributions to the Enso org repo improving interpreter features, method dispatch and low-level performance—with product-level vision for real-time collaborative developer platforms. Based in Lisbon with roots in Poland and a theoretical computer science background from Jagiellonian University, he blends academic rigor with startup execution. Notably, his work emphasizes pragmatic performance techniques (tail recursion, unboxed representations) paired with strong testing discipline, making him comfortable tackling problems most teams avoid.
14 years of coding experience
7 years of employment as a software developer
The 5th High School in Kraków, PolandBachelor's degree Theoretical Computer Science, Bachelor's degree Theoretical Computer Science at Jagiellonian University
Polish, English
Stackoverflow
575reputation
136kreached
6answers
33questions
Github Skills (13)
programming-language10
compiler-design10
architectures10
architecture10
testing10
build-tools9
autocomplete6
html6
transparency6
css6
curl6
winapi6
autoit6
Programming languages (21)
Github contributions (5)
enso-org/enso
Jun 2019 - Jan 2023
Enso Analytics is a self-service data prep and analysis platform designed for data teams.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:436 reviews, 206 commits, 213 PRs in 3 years 8 months
Contributions summary:Marcin has been actively involved in enhancing Enso's interpreter, focusing on core language features and performance optimizations. Key contributions include implementing string literals, datatypes, and improving method dispatch. They've also addressed performance by applying techniques such as tail recursion and unboxed atom representations while maintaining a strong focus on testing.
dataprepvisualcompilerhybridenso
reilabs/gnark-lean-extractor
Aug 2023 - Apr 2025
A tool to extract gnark circuits defined in Go to Lean for formal verification.
Contributions:7 releases, 11 reviews, 1 PR in 1 year 7 months
formal-verificationgnarkgo
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