Kacper Madej
Staff Software Engineer at Castle
Krakow, Lesser Poland Voivodeship
Summary
🤩
Rockstar🎓
Top SchoolKacper Madej is a Staff Software Engineer based in Krakow with 13 years of experience building robust, high-throughput backend systems and APIs, primarily in Ruby and Rails. He excels at pragmatic problem solving and architectural improvements that increase performance and reliability—evidenced by migrations from Postgres to Aerospike, introducing circuit breakers, and reducing integration times from weeks to minutes. Kacper combines hands-on delivery with observability and CI/CD best practices, having added app performance monitoring and business-specific tracing for production systems handling thousands of events per second. He also contributes to low-level database work in the open-source limbo project, implementing JSON functions and core SQL features while improving identifier handling and refactoring core logic. Comfortable across the stack, he has a track record of optimizing ETL and batch workloads, speeding up large XLSX generation and parallelizing CI pipelines. Pragmatic, curious, and systems-minded, he thrives on turning complex data challenges into maintainable, testable solutions.
12 years of coding experience
9 years of employment as a software developer
Bachelor of Engineering (B.E.), Computer Science, 4.5, Bachelor of Engineering (B.E.), Computer Science, 4.5 at AGH University of Science and Technology in Cracow
English, Polish
Github Skills (9)
json10
databases10
better-sqlite310
rust10
sqlite10
embedded-database10
sql10
database10
webassembly9
Programming languages (11)
Github contributions (5)
tursodatabase/limbo
Dec 2024 - Jan 2025
Limbo is a project to build the modern evolution of SQLite.
Role in this project:
Back-end Developer & Database Engineer
Back-end Developer & Database EngineerContributions:30 reviews, 6 PRs, 44 comments in 1 month
Contributions summary:Kacper's primary contribution revolves around enhancing the `limbo` project, which is focused on building a modern evolution of SQLite. Their work involved significant changes to the core database logic, including implementing JSON-related functionalities such as `json_array`, `json_extract`, `json_type` and operators. The commits show a focus on improving identifier handling, code refactoring, and the implementation of features that enhance the project's capabilities for SQL database interactions with JSON.
databaseembedded-databasesqlsqlite3webassembly
u2i/email-validation
Feb 2015 - Jan 2017
Contributions:7 PRs, 18 pushes, 6 branches in 1 year 11 months
ruby-gememailsrubytradegem
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