Jung Sup (Jay) Yoo

Software Engineer | Incident Management & Customer Implementation | Korean, English, Japanese

Fukuoka, Japan

LinkedIn
JSY

About

Software engineer with 8+ years across reliability engineering, DevOps, and client consulting. Spent 5+ years as incident manager for 200+ critical customer incidents at a global enterprise SaaS, working live with support, sales, solutions engineers, and customers, and has owned customer implementations end to end, from discovery through delivery and ongoing support. Hands on with Kubernetes, AWS, Cloudflare, and AI assisted automation. Native Korean speaker, fluent in English, and fluent in Japanese (JLPT N1).

Work Experience

Rakuten Group, Inc.
Office

2026 - Present

Application Engineer, assigned to Rakuten Payment

  • Own end to end troubleshooting of production payment errors, including network failures, dropped connections, and expired batch machines, debugging logs and analyzing system behavior to resolve issues directly.
  • Building an MCP plugin that adds multilingual support to engineering documentation as it is written and updated, supporting the company's English first initiative.
  • Scoped to lead production setup for an upcoming merchant onboarding with implementation and support teams, enabling Rakuten Point payments through POS terminals.

Deltek | Replicon
Remote

2021 - 2026

Senior Software Engineer (Site Reliability Engineering)

  • Served as incident manager for 200+ critical customer incidents across NA and APAC, including weekend and holiday on call, leading live calls with support, sales, solutions engineers, and customers and calmly steering tense escalations to resolution.
  • Wrote customer readable RCAs and walked sales and CS teams through the technical details, then partnered with the core product team to ship permanent fixes, so similar cases went straight to the product team instead of becoming incident calls.
  • Modernized a core service from .NET Framework on Windows to .NET 6 on Kubernetes, cutting AWS costs by 30%, and built an AI assisted modernization workflow that shortened a 3+ year migration plan by nearly two years.
  • Led the network migration to Cloudflare, owning DNS, WAF, caching, and traffic routing, which strengthened DDoS mitigation while maintaining 99.99% uptime.
  • Provisioned and maintained AWS infrastructure across 8+ regions with Terraform and operated multi region production Kubernetes clusters for an ERP platform used by millions of enterprise and government users.
  • Built a Quality of Service and SLO platform from scratch, standardizing SLO attainment, p95 and p99 latency, and Sev1 and Sev2 trends behind a 99.99% target tied to customer SLAs.
  • Led an HSM backed code signing pipeline for FIPS compliance and remediated recurring penetration test findings with security and product teams.
  • Built n8n automations on the OpenAI API that reviewed code changes and production configuration update memos before they reached production.
  • Authored runbooks for Cloudflare, Kubernetes operations, and an AI assisted .NET modernization workflow, adopted by an SRE team of 20, and mentored junior SREs.

Vigouth Pte. Ltd.
Remote

2024 - 2025

Co-founder & Director (Part time)

  • Onboarded SEA based clients as technical point of contact, defining scope, milestones, and success metrics.
  • Built AI driven content and marketing pipelines, integrating generative tooling into team workflows to speed up turnaround.
  • Ran production for YouTube content and a print on demand portfolio targeting North America, coordinating designers and editors to deliver on schedule.

Chy Square Inc.
Remote

2019 - 2024

Founder & Technical Consultant

  • As sole operator, owned every client relationship end to end, from discovery through delivery and ongoing operational support, handling issues and change requests directly with clients.
  • Built an SEO focused marketing website for an overseas boutique law firm, working directly with its Korean speaking owner.
  • Partnered with a marketing agency on development projects, surfacing needs clients had not stated.

Indeed
Remote

2018 - 2019

INTL General Research Team Member

  • Developed a Chrome extension using JavaScript and jQuery to streamline data extraction and transformation workflows, improving operational efficiency by up to 75%.
  • Collected job postings from Korean job boards and converted them into structured records for Indeed's database.

WOORI Education & Immigration Consulting
Office

2019 - 2019

Case Processing Assistant

  • Worked directly with clients to identify their biggest concerns, then prepared documentation addressing them so applications were filed by their deadlines and approved without setbacks.
  • Processed 200+ Canadian visa applications monthly with the team and built a Python tool that cut daily administrative workload by over 40%.

Education

University of Toronto, St. George

2014 - 2017
H.B.Sc, Economics and Statistical Science

Skills

Kubernetes
Site Reliability Engineering
Observability
Prometheus / Grafana
Docker
Terraform
Cloudflare
AWS
Argo CD / GitOps
Jenkins
Networking & Security
Python
JavaScript / TypeScript
C#
CI/CD
PostgreSQL
Linux
DevOps

Projects

Unlyst

World's first marketplace for off-market homes: Unlyst is a crowd-sourced valuation marketplace that uses the wisdom of crowds to capture market sentiment and real-time home values.

Side Project
TypeScript
Next.js
Tailwind CSS
Supabase
AWS

Chilluck

A blog sharing latest updates of immigration policies for expats in the world

Side Project
TypeScript
Next.js
Tailwind CSS
Supabase

Jasan

Tracking price trend of stocks in US and Korean market

Side Project
Python
Next.js
Postgres
Supabase

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