René Schwietzke

CEO and co-founder of Xceptance. René has served as Xceptance’s Managing Director since 2004 including the continuous evaluation and development of test tools and services. He holds a Master’s degree in Computer Science from Brandenburg University of Technology, Germany.

He has been working with Java since version 1.0. While working with and for two ecommerce and one quality assurance company, he gained plenty of insides into Java, performance tuning, and performance measurements that includes but is not limited to JIT, GC, and the JMM.

René regularly gives talks and training about programming in Java, GC and memory management, as well as testing and quality assurance.

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Jakarta EE 11: Beyond the Era of Java EE

This user guide provides a brief history of Java EE/Jakarta EE and a detailed overview of some of the specifications that will be updated in Jakarta EE 11.

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The Curious Case of Different Runtimes

Strange runtime behavior when presenting different training data to the JIT. We show how we diagnosed and condense down to a few test cases.

Jun 30 3,5K

René Schwietzke

Performance

Use Cases

Retweet on Twitter Foojay.io Retweeted

Wow, @spring_io was a blast this year! Reunited with my friends, made some new friends, and had a friendly staged fight with my partner-in-crime @asm0di0 over JPA and jOOQ. Thank you, @sergialmar , for organizing this amazing event!

10:37 AM · April 17, 2026

Retweet on Twitter Foojay.io Retweeted

Interesting read on @foojayio about the current state of the @grailsframework, at @TheASF
Written by @spoole167 interviewing @JamesFredley
https://foojay.io/today/grails-isnt-done-yet-part-1-inside-the-asf-reboot/

11:31 AM · March 25, 2026

Retweet on Twitter Foojay.io Retweeted

#Java 26 is here, and its main purpose is to provide a solid foundation for future things to come. It comes with new features, performance improvements and multiple enhancements–my blog post has all the info! 🚀

07:15 AM · March 17, 2026