Mariusz Krzemień - Senior Software Developer at SoftwareMill

Mariusz Krzemień

Senior Software Developer at SoftwareMill

Cracow Metropolitan Area Poland

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Summary

🤩

Rockstar

🎓

Top School

Mariusz Krzemień is a Senior Software Developer with over 10 years of experience building distributed Java and Scala systems, currently shaping telecom value-added services at SoftwareMill. He combines deep backend expertise (Spring Boot, Akka, Apache Flink) with practical data and ML tooling (Spark, BigQuery, Keras/TensorFlow exposure) and solid deployment skills using Docker and Kubernetes. His background spans finance and telecom domains, where he led functional analysis, design and technical analysis across agile teams. An active contributor to notable open-source Scala projects, he improved Tapir's OpenAPI generation and enhanced observability in the sttp HTTP client via Prometheus/OpenTelemetry tests. Fluent in English and experienced across databases (MySQL, MongoDB, Oracle) and test automation, he brings an engineer’s rigor to documentation and monitoring as much as to core business logic. Based in the Cracow area, he pairs long-term enterprise experience with a continual focus on API accuracy and runtime observability.

10 years of coding experience

13 years of employment as a software developer

IV Liceum Ogólnokształcące w Bielsku-Białej

Master of Science, Computer Science, Master of Science, Computer Science at Jagiellonian University

Github Skills (18)

testing10

akka-http10

scala10

http-client10

prometheus10

opentelemetry10

functional-programming10

openapi10

documentation10

api-design9

http9

api9

reactive-streams8

typesafe8

type-safety8

Programming languages (2)

JavaScala

Github contributions (5)

softwaremill/tapir

Feb 2022 - Jun 2022

Rapid development of self-documenting APIs

Role in this project:

Back-end Developer

Contributions:15 reviews, 33 commits, 52 PRs in 4 months

Contributions summary:Mariusz primarily focused on enhancing the documentation generation capabilities of the `tapir` library, specifically concerning OpenAPI specifications. They implemented and tested features related to default values for request bodies and query parameters within OpenAPI documentation. These changes included tests for enum types and workarounds for encoding defaults, demonstrating a focus on improving the accuracy and completeness of the API documentation generated by the library. The commits directly address issues related to the OpenAPI documentation generation process.

functional-programmingendpointsobservabilityhttp4ssttp

softwaremill/sttp

Jun 2022 - Jun 2022

The Scala HTTP client you always wanted!

Role in this project:

Back-end Developer & Test Automation Engineer

Contributions:8 reviews, 12 commits, 4 PRs in 6 days

Contributions summary:Mariusz primarily contributed to the observability features of the `sttp` library, specifically focusing on Prometheus and OpenTelemetry integrations. They added and modified test cases to validate the behavior of these backends, including scenarios involving HTTP errors and exceptions. The commits demonstrate a strong understanding of how to instrument and monitor HTTP client interactions within the `sttp` framework using metrics.

guzzlefinaglehttpclientfs2zio

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