Dariusz Jędrzejczyk
Principal Engineer at Model Context Protocol
Krakow, Lesser Poland Voivodeship
Summary
🤩
Rockstar🎓
Top SchoolDariusz Jędrzejczyk is a Principal Engineer and long-time contributor to the Spring ecosystem, currently leading Reactor Core work at Broadcom and co-maintaining the MCP Java SDK. With 12+ years delivering high-load backend, mobile and data-processing systems, he combines deep expertise in concurrency, networking and distributed systems with a pragmatic focus on performance and developer productivity. He has driven core improvements in widely used open-source projects such as Reactor and ServiceTalk and implemented advanced distributed features like Hermes’ consumer rate negotiation backed by ZooKeeper. A frequent speaker and trainer, he values maintainable code, robust architecture and proven engineering practices—often translating that into shared frameworks used by hundreds of engineers. Quietly pragmatic, he balances hands-on low-level JVM and networking fixes with leadership that shapes collaboration and production reliability across large teams.
12 years of coding experience
11 years of employment as a software developer
MSc, Computer Science, MSc, Computer Science at Jagiellonian University
English, Spanish, Polish
Stackoverflow
901reputation
54kreached
13answers
5questions
Github Skills (32)
netty10
messaging10
multithreading10
http10
kafka10
distributed-systems10
zookeeper10
java10
javas10
reactive-programming10
pubsub10
grpc10
concurrency10
testing9
tls129
Programming languages (8)
Github contributions (5)
allegro/hermes
Feb 2016 - Jun 2018
Fast and reliable message broker built on top of Kafka.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:17 commits, 49 PRs, 124 pushes in 2 years 4 months
Contributions summary:Dariusz contributed significantly to the `hermes` message broker, focusing on features related to consumer rate negotiation and management. Their work involved implementing a max rate negotiation algorithm using Zookeeper for rate history storage, demonstrating expertise in distributed systems. The commits also show contributions to the administration scripts and the implementation of eager loading for a core registry component. Additional contributions show the user's work on rate limiting applying only to the local Data Center.
brokermessage-queuehermesmessage-brokerreliable
apple/servicetalk
May 2021 - Apr 2022
A networking framework that evolves with your application
Role in this project:Back-end Developer
Back-end DeveloperContributions:5 releases, 208 reviews, 92 commits in 11 months
Contributions summary:Dariusz focused on improving the `servicetalk` framework by adding support for wrapping read-only `ByteBuffer` objects within the `ServiceTalkBufferAllocator`, ensuring compatibility with read-only direct buffers. Furthermore, the user contributed to the `http-netty` module by adding new methods for configuring TLS settings like peer host inference and SNI host name inference for HTTP and GRPC clients. Additionally, the user refactored the build system for load balancing with DNS based discovery. This improved the overall stability, reliability, and network performance of the framework.
rpcgrpchttp2frameworkreactive-streams
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