Karol Sobczak
Data And Performance Engineering At Scale
Warsaw, Masovian Voivodeship, Poland
Summary
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Rockstar🎓
Top SchoolKarol Sobczak is a seasoned data and performance engineer with 15 years of experience tuning distributed SQL engines and building scalable database systems. Based in Warsaw, he has been a Trino maintainer and a founding engineer at Starburst, contributing deep optimizations to Presto/Trino core components such as query planning, dynamic filters, and memory accounting. At Apple he now applies that production-scale performance expertise to data and performance engineering at scale. His work spans low-level execution improvements, optimizer enhancements, and robust testing/benchmarking frameworks developed during his time at Teradata and earlier research roles. An active open-source contributor, he has implemented ODBC-compliant features and subtle concurrency fixes in the widely used Presto/Trino engines—efforts that directly impact large-scale analytics clusters. With a strong academic background in computer science and practical experience from kernel-level experiments to high-performance Java libraries, he combines rigorous engineering with measurable system impact.
15 years of coding experience
14 years of employment as a software developer
Master of Science (MSc) Computer Science, Master of Science (MSc) Computer Science at Vrije Universiteit Amsterdam (VU Amsterdam)Master of Science (MSc) Mathematics and Computer Science (JSIM), Master of Science (MSc) Mathematics and Computer Science (JSIM) at University of Warsaw
English, German
Stackoverflow
21reputation
419reached
1answer
0questions
Github Skills (12)
javas10
performance-optimization10
sql10
back-end-development10
java10
data-engineering10
testing9
distributed-systems7
kubernetes6
starburst6
presto6
kubernetes-pods6
Programming languages (8)
Github contributions (5)
trinodb/trino
Aug 2022 - Jan 2023
Official repository of Trino, the distributed SQL query engine for big data, formerly known as PrestoSQL (https://trino.io)
Role in this project:
Back-end Developer
Back-end DeveloperContributions:4175 reviews, 89 commits, 1761 PRs in 4 months
Contributions summary:Karol made several code changes in the Trino project, focusing on enhancing the system's functionalities. They addressed synchronization issues in the RaptorSplitManager, improved error messages, and ensured proper initialization of lazy dynamic filters. The user also contributed to the improvement of dynamic filter extraction and optimization of the join operator's behavior. Moreover, the user added more tests to verify the core functionality of the system, including tests for a number of edge cases.
prestodbdbmsindexingjdbcbigdata
prestodb/presto
Jul 2015 - Aug 2019
The official home of the Presto distributed SQL query engine for big data
Role in this project:Back-end Developer
Back-end DeveloperContributions:394 commits, 300 PRs, 94 pushes in 4 years 2 months
Contributions summary:Karol primarily worked on enhancing the Presto distributed SQL query engine. Their contributions included implementing a feature to support multiple arguments for the CONCAT string function, which ensured compliance with the ODBC standard. In addition, the user addressed issues within the query queueing system by implementing the use of `decrementAndGet` in the reserve method and providing updates to the related documentation. The user further contributed by measuring peak memory usage for stage tasks.
distributed-sqlquerybigdataquery-enginesql
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