Sungjin Lee
Software Developer at 카카오엔터프라이즈 (Kakao Enterprise)
Saemkkumi, Gyeonggi, South Korea
Summary
🤩
Rockstar🎓
Top SchoolSungjin Lee is a software developer with nine years of experience specializing in distributed systems and observability, currently building cloud-native infrastructure at Kakao Enterprise. He is a maintainer-level contributor to the CNCF Cortex project, where he added query execution metrics (including cortex_query_samples_total) and enhanced ruler query statistics to improve Prometheus long-term storage observability. With a master's in computer science from KAIST and a bachelor's from Pusan National University, he blends strong academic grounding with practical production engineering. Based in Gyeonggi, South Korea, Sungjin focuses on backend Go development and performance instrumentation for large-scale multi-tenant systems. Peers describe him as someone who turns low-level telemetry into actionable insights, helping teams make data-driven reliability improvements.
9 years of coding experience
학사 정보컴퓨터공학부, 학사 정보컴퓨터공학부 at Pusan National University석사 전산학부, 석사 전산학부 at Korea Advanced Institute of Science and Technology
Github Skills (5)
go10
prometheus10
promql9
kubernetes8
kubernetes-pods8
Programming languages (3)
Github contributions (5)
cortexproject/cortex
Aug 2024 - Apr 2025
A horizontally scalable, highly available, multi-tenant, long term Prometheus.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:120 reviews, 93 PRs, 232 comments in 7 months
Contributions summary:Sungjin contributed to the Cortex project by adding metrics and statistics related to query execution. They implemented a new metric, `cortex_query_samples_total`, and integrated it into the query frontend handler and the ruler. These changes involved modifying Go code within the `pkg/frontend/transport/handler.go` and `pkg/ruler` directories to track and report query performance metrics. The user also added a metadata query function and applied metrics to the ruler query stats.
golangscalabletenantprometheus-exporterlong-term
SungJin1212/promql-engine
Dec 2024 - Apr 2025
Multi-threaded PromQL engine implementation based on the Volcano paper.
Contributions:76 pushes, 7 branches in 3 months
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