Marcin Grzejszczak
Software Engineer at HeroDevs
Warsaw, Masovian Voivodeship, Poland
Summary
🤩
Rockstar🎓
Top SchoolMarcin Grzejszczak is a seasoned Java software engineer and Java Champion with 13+ years building cloud-native systems, observability, and testing tooling. A former Spring Engineering Team member and long-time contributor to Spring projects (Spring Cloud, Spring Boot, Micrometer, Spring Cloud Contract), he blends deep backend instrumentation work with DevOps and CI/CD automation. He founded iurista.org, co-authored SmartTesting, and maintains multiple open-source projects while creating courses and conference talks that influence the Java ecosystem. His contributions span high-impact repos like spring-boot and mockito, where he improved tracing, context propagation, and testing robustness. Known for pragmatic engineering, he often fixes subtle startup and integration issues and automates documentation and release pipelines across projects. Based in Warsaw, he pairs hands-on code-level fixes with system-wide process improvements, making complex distributed systems easier to test and operate.
13 years of coding experience
14 years of employment as a software developer
MSc, Telecommunications and Computer Science, MSc, Telecommunications and Computer Science at Lodz University of TechnologyDanmarks Tekniske Universitet
English, French, Spanish
Stackoverflow
10,933reputation
742kreached
547answers
3questions
java
top-5%
spring
top-5%
spring-cloud
top-1%
spring-boot
top-1%
Github Skills (95)
testing10
microservices-application10
bash10
instrumentation10
zookeeper10
javas10
java-libraries10
consul10
automation10
infrastructure10
automation-testing10
build-automation10
maven10
wiremock10
opentelemetry10
Programming languages (16)
Github contributions (5)
spring-attic/github-analytics
Apr 2016 - Jul 2018
GitHub Analytics app. Analyses GitHub messages received from Github Webhook app. Part of the deployment pipeline example
Role in this project:
Back-end Developer & DevOps Engineer
Back-end Developer & DevOps EngineerContributions:108 commits, 6 PRs, 63 pushes in 2 years 3 months
Contributions summary:Marcin primarily contributed to enhancing the GitHub Analytics application, with a focus on backend and deployment aspects. Their work included adding and integrating Accurest for stub testing. Furthermore, the user modernized the project by upgrading the Spring Boot version and dependencies, and they added REST endpoints and integration tests for enhanced functionality and reliability. They also added service discovery feature.
spring-attic/spring-cloud-pipelines
Oct 2016 - Nov 2018
[DEPRECATED] Codebase containing Concourse and Jenkins opinionated pipelines. Moved to https://github.com/CloudPipelines/
Role in this project:DevOps Engineer & Backend Developer
DevOps Engineer & Backend DeveloperContributions:9 releases, 477 commits, 78 PRs in 2 years 1 month
Contributions summary:Marcin was primarily involved in setting up and maintaining the CI/CD pipeline using Jenkins, Docker, and cloud-based deployments. They migrated the project to use Spring Cloud and updated deployment configurations, including setting up new dependencies. They also made modifications to backend code in Groovy and other languages, while also managing and maintaining the existing build configuration.
jenkinsspring-cloud-core
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