Why I replaced an eight-second confirmation request with an asynchronous intent
A write-path redesign that released Tomcat request threads immediately and fixed an overly broad rule that could supersede unrelated pending approval actions.
Hello, I am software engineer Hong Seong Ju.
I document what I learn by building.
I build backend, data, and AI systems. These notes preserve the constraints, failed hypotheses, decisions, and evidence behind the result—not only the finished screen.
Recent writing
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Validating Cilium FQDN egress without touching a single-node production cluster
A disposable kind lab that proved identity-specific toFQDNs and Hubble drops while keeping the risky production CNI migration behind an explicit gate.
Why a public ALB still had to be closed behind CloudFront
A zero-downtime origin lockdown that moved the BFF first, then restricted direct ALB HTTP access to AWS-managed CloudFront origin-facing networks.
A GitOps deadlock between a new readiness probe and an old image
GitHub redirected the repository but not the GHCR coordinate, so Argo CD combined a new /ready probe with an image that could only return 404.
Designing Kafka consumer groups when every Pod must receive an SSE event
A cutover from lightweight database notifications to Kafka KRaft, including broadcast semantics, a duplicate-bean rollout failure, and a live broker interruption.
Why I trust runnable tags instead of node names in a LangGraph SSE stream
A streaming and routing repair for real event metadata that differed from mocks, leaked tool preambles, and let stale turns influence new routes.
Featured projects
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ssuAI, ssuMCP, ssuAgent, and ssu-ai-service connect Soongsil University data to the web, natural-language agents, and standard MCP tools in an operating platform.
Personal project · Designed, implemented, and operate 4 services
MCPLangGraphSpring BootNext.js
02
Geuneul — Summer Survival Map
CompleteA map service that combines more than 150,000 public POIs, PostGIS spatial search, and real-time reports to help people find nearby shelter during heat waves and rain.
Personal project · End-to-end ownership of product, data, backend, and infrastructure
Spring BootPostGISNext.jsPWA
03
UNITHON Voice Kiosk Macro
CompleteA Windows accessibility-retrofit prototype that turns a voice order into semantic actions on a third-party kiosk and stops at a verified payment-method screen without modifying the kiosk source.
Competition · Voice client, semantic UI automation, and safe order handoff
PythonWindows UIAEasyOCRSQLite