Winter Jung(정겨울)

Karrot

2024.04–Present, Seoul

2024.04–Present

Saved ~$1M+/year by redesigning the feature logging pipeline (Kafka → Go consumer → GCS → BigQuery batch load) handling 3GB/s of recommendation event traffic, scaling to 4.5x growth with stable operation.
Built and operate a production LLM pipeline (2T+ tokens processed) that classifies marketplace listings into 10,000+ category taxonomy with attribute extraction. Reduced LLM costs by 90% through embedding-based pre-filtering, prompt caching, and hybrid retrieval (BM25 + semantic search). Designed LLM-as-a-Judge evaluation framework for continuous quality monitoring.
Operated the feature store and recommendation engine powering Karrot's home feed — serving 10M+ daily requests at p999 <30ms. Led set type support enabling carousel-based recommendations.
Speaker at GopherCon Korea 2024: "Deterministic Testing in Go"

2018.11–2023.09, Seoul

2022.01–2023.09

Contributed 15+ packages as the first committer to an in-house Go library used by 50+ repositories.
Over 3 years, developed a gRPC project generator, an IDL repository (a company-wide API interface repo based on Protocol Buffers), and a DDL repository (a DB schema repo).
Reviewed 10K+ GitHub PRs across 120+ repositories. Consistently ranking #1 in code reviews annually. Reviewed technical specifications for 20+ server engineers, ensuring code quality and optimal implementation.
Reduced p99 latency by 90%, queries by 95% and RDS CPU peak by 15%p for the core service that performed 260M queries/day by adding Redis and in-memory cache layer.
Reduced monthly costs by 80% by migrating a single MySQL table with 70TiB and 26 billion rows into AWS Athena.
Over 2 years, shut down 16 legacy services and removed 250+ legacy API endpoints.
Planned and operated the server chapter onboarding process for over two years.

2018.11–2021.12

Participated as a tech lead in the MyData server development project, handling 100M daily traffic from 250+ financial companies. Managed performance improvements and issue resolutions for over 2 years.
Migrated 130+ self-hosted Kubernetes services to AWS EKS with no downtime to comply with MyData security requirements.
Decomposed 200+ monolithic legacy APIs built on Python, MongoDB into 15 microservices based on Golang, MySQL, and gRPC with dual-write and shadowing.
Increased the financial card company integration by 318% and the Korea-government tax service integration by 868% by developing the year-end tax reconciliation algorithm.
Built a new ChatOps CI/CD pipeline, reducing deployment steps by 80% and increasing production deployments by 400% per week.
Built a zero-downtime deployment system based on VMs and L4 switches in a private cloud IDC using Packer and Ansible.
Established a company-wide Python style guide.

2018.03–2018.09, Seoul

2018.03–2018.09

Developed a Telegram bot to process voice data asynchronously for improving STT.
Developed a Python RESTful API using AWS ECS, websocket and a message queue.

Bachelor of Science in Urban Engineering

2014–2024, Seoul