Kim, Joo Hyuk
Server Developer (Toss Core) at Viva Republica (Toss)
Seoul, South Korea
Summary
🤩
Rockstar🎓
Top SchoolKim Joo Hyuk is a server-focused backend engineer with six years of experience building reliable, event-driven systems and scalable core services, currently driving Toss Core initiatives in Seoul. He contributes to major open-source projects like Apache Pulsar—improving Java client thread-safety—and is a core contributor to FasterXML’s Jackson project, helping steward the Jackson 3 release. His background includes designing next-generation localization for an international product and pioneering exactly-once delivery with Kafka for banking-reporting systems. Comfortable moving between high-impact product work and low-level concurrency fixes, he blends production-grade engineering with open-source sustainability. An unconventional detail: his academic background in physical therapy informs a pragmatic, systems-thinking approach to troubleshooting and resilient design.
6 years of coding experience
Bachelor of Science - BS, Physical Therapy, Bachelor of Science - BS, Physical Therapy at De La Salle Medical and Health Sciences Institute
Stackoverflow
88reputation
916reached
2answers
2questions
Github Skills (22)
messaging10
back-end-development10
multithreading10
pulsar10
java10
javas10
thread10
hyper-threading10
threaded10
pubsub10
cli8
command-line-interface8
command-line8
event-streaming8
queuing8
Programming languages (7)
Github contributions (5)
apache/pulsar
Jun 2023 - Nov 2023
Apache Pulsar - distributed pub-sub messaging system
Role in this project:
Back-end Developer
Back-end DeveloperContributions:3 reviews, 1 PR, 12 comments in 5 months
Contributions summary:Kim, primarily focused on improving the Java client for the Apache Pulsar messaging system, addressing thread-safety issues within the consumer implementation. They modified the ConsumerImpl class to make seek operations thread-safe and documented the changes. Additionally, they contributed to fixing a class name typo within a broker test and enhanced the CLI by allowing for the creation of replicated subscriptions. Further contributions include administrative tool updates to address exit code errors in source commands and improvements to broker configurations.
event-streamingpulsarmessaging-systemstreamingapache
JooHyukKim/jackson-databind
Jan 2023 - Mar 2025
General data-binding package for Jackson (2.x): works on streaming API (core) implementation(s)
Contributions:10 PRs, 331 pushes, 244 branches in 2 years 2 months
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