FIELD NOTE · E5 · Feb 2023 – Feb 2026
From a monthly security review to a daily automatic one
Replaced a multi-day manual month-end review of four clouds with a daily automatic one that surfaces risky actions the same day.
Read the note ↗CLOUD INFRASTRUCTURE & SECURITY ENGINEER ↘
I turn infrastructure and security that relied on people's memory into structures that code protects.
From live games to financial services, running infrastructure across 4 clouds (AWS, GCP, Azure, and Tencent), at up to 3,500 servers and 650 databases. I have experience cutting deployment time by 40% by moving to Terragrunt and raising CSPM (cloud security posture checks) remediation from 60% to 85% or higher.
See selected work- 3,500
- Servers run as the dedicated engineer
- 40%
- Shorter deployment time
-
60%85%+ - Audit remediation rate
- 0
- Downtime during migration
01 / IMPACT FIRST
Selected work
Results you can check in numbers come first. Open a row for the full case.
- 01
Woori FIS · AWS · Security · Feb 2026 – Oct 2026
Woori Financial Group AWS security architecture
5 Security services connected to Splunk SIEM/SOAR · 3 Design principles from network separation · 1 Set of Terraform code across multiple AWS accounts
Moved network separation requirements across multiple AWS accounts into subnet and firewall structure, and standardized security settings as one set of Terraform code.
Terraform · AWS Network Firewall · AWS WAF · AWS Shield Standard · GuardDuty · Security Hub · Splunk · Python Details → - 02
Com2us Platform · Migration · Feb 2023 – Feb 2026
Zero-downtime migration from GCP to Tencent Cloud
80 Servers migrated · 20 Databases migrated · 0 Downtime
Moved 80 servers and 20 databases of Summoners War: Chronicles from GCP to Tencent Cloud in about one week with no downtime.
Terraform · GCP · Tencent Cloud · Online Migration Details → - 03
PF-04 · AWS · Terragrunt · Personal project · released Nov 2026
AWS Terragrunt DRY IaC
16 Terraform modules and units · 1 Root config replacing 16 copies · -40% Deployment time (production result)
Sixteen Terraform modules behind one root config, with Terragrunt running them in order from their dependency graph.
Terragrunt · Terraform · AWS Details → - 04
C&Thoth · Azure MSP · Jul 2021 – Feb 2023
MIR4 Global: massive Azure infrastructure and automated DDoS blocking
3,500 Servers · 650 Databases · 0 Human steps from detection to block
Dedicated operation of a global game with 3,500 servers and 650 databases on Azure, plus a pipeline that finds DDoS sources in logs and adds them to an NSG automatically.
Azure · Dedicated Host · PowerShell · Log Analytics · NSG Details →
More cases
- AWS multi-region Terraform 16 regions PF-01 · AWS · IaC
- GCP Terraform GKE platform 22 modules PF-02 · GCP · IaC
- Tencent Cloud audit-ready Terraform 4 audit tracks PF-03 · Tencent · IaC
- Multi-cloud asset and audit automation 3 clouds PF-05 · Multi-cloud · Python
- AetherCrew: a virtual company of 11 AI employees 11 AI employees PF-06 · AI · FastAPI
- AWS firewall request automation 3 steps PF-09 · AWS · Python
- Summoners War: Sky Arena multi-cloud and firewall redesign 600 / 70 Com2us Platform · Multi-cloud
- Dragon Sky FinOps: 62% lower infrastructure cost Up to -62% Com2us Platform · FinOps
02 / CAPABILITIES
What I can own
Keywords are the tools actually used in each area’s cases.
-
IaC automation
Define infrastructure as code with Terraform and Terragrunt
Terraform · AWS · EKS · CloudWatch · AWS Chatbot · GCP · GKE · Cloud Logging
-
Multi-cloud operations
Design and operate 4 cloud providers together
Python · boto3 · Google Cloud SDK · Tencent Cloud SDK · Google Sheets · Slack · Telegram · Terraform
-
Cloud security
Detection and response, least privilege, and audit response
Terraform · Tencent Cloud · CloudAudit · COS · CAM · CLB · Python · boto3
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Operations automation · AI agents
Remove repetitive work with Python and PowerShell. Build multi-agent systems with defined roles and permissions
Python · boto3 · Google Cloud SDK · Tencent Cloud SDK · Google Sheets · Slack · Telegram · FastAPI
03 / FIELD SIGNAL
Proof from the field
Check it in the field notes, the public code and the certifications.
Public repos
- pf-01-aws-terraform-multi-region ✓ v1.0.0 · CI passing
- pf-02-gcp-terraform-gke-platform ✓ v1.0.0 · CI passing
- pf-03-tencent-terraform-audit-ready ✓ v1.0.0 · CI passing
- pf-04-aws-terragrunt-dry-iac ✓ v1.0.0 · CI passing
- pf-05-multicloud-asset-audit-automation ✓ v1.0.0 · CI passing
- pf-06-aethercrew-ai-company ✓ v1.0.0 · CI passing
- pf-09-aws-netops-firewall-automation ✓ v1.0.0 · CI passing
Certifications
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NCP — Naver Cloud Platform Certified Professional Valid · 2021.08.18
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NCA — Naver Cloud Platform Certified Associate Valid · 2021.07.07
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Engineer Information Processing (Korean national certification) Valid · 2021.06.02
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Microsoft Azure Fundamentals (AZ-900) Valid · 2020.10.22
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Linux Master Level 2 Valid · 2019.10.11
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Network Administrator Level 2 Valid · 2019.07.09
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HashiCorp Certified: Terraform Associate Expired · 2022.12.18
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CKA — Certified Kubernetes Administrator Expired · 2022.12.16
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Microsoft Azure Database Administrator Associate Expired · 2022.06.09
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Microsoft Azure Solutions Architect Expert Expired · 2022.06.08
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Microsoft Azure Administrator Associate Expired · 2022.06.07
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AWS Certified Solutions Architect – Professional Expired · 2022.05.29
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Microsoft Azure Architect Technologies Expired · 2021.07.01
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Microsoft Azure Security Engineer Associate Expired · 2021.06.18
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AWS Certified Solutions Architect – Associate Expired · 2020.06.23
All field notes (24)
- E1 Dedicated engineer for a 3,500-server global game
- E2 Stopping 3 a.m. DDoS attacks with no one on the keyboard
- E3 Deploying to 500 servers, 80% faster
- E4 Infrastructure status at a glance, in real time
- E5 From a monthly security review to a daily automatic one
- E6 Making sure the same finding never comes back
- E7 One codebase instead of copied infrastructure code
- E8 Moving a live game between clouds without stopping it
- E9 Redesigning a tangle of firewall rules
- E10 Stopping attacks on game servers
- E11 Knowing first when something goes wrong
- E12 An AI that writes infrastructure code from a plain request
- E13 Setting a security baseline for a financial cloud that had none
- E14 Only the access you need, recorded in code
- E15 Alerts from many accounts on one screen
- E16 "Turned on" and "actually blocking" are different things
- E17 Operations tools that run on a PC with no internet
- E18 Explaining in the language the other person already knows
- E19 Less time spent capturing packets
- E20 Owning the security checks that repeat every month
- E21 A security review that tested requirements with numbers
- P1 A virtual company staffed by 11 AI employees
- P2 A service that answers "can these two talk?" in two clicks
- P3 A public repository series for this portfolio
04 / CONTEXT
Experience & education
Most recent first.
- Feb 2026 – Oct 2026
Woori FIS — Assistant Manager · Cloud Security Engineer
Information Security Department · Designed and completed Woori Financial Group's first cloud security policy definition after joining, and distributed it to the group's affiliates
- Feb 2023 – Feb 2026
Com2us Platform — Assistant Manager · Cloud Engineer
Infrastructure Technology Office, Cloud Division · Cut deployment time by 40% by moving from Terraform to Terragrunt
- Aug 2020 – Feb 2023
C&Thoth — Associate to Assistant Manager · Cloud Engineer (Azure MSP)
Cloud Service Team · Ran Azure infrastructure for many game services in Korea and worldwide, including dedicated operations for MIR4 Global (3,500 servers and 650 databases)
Education · training · service
- Mar 2015 – Feb 2020
Kyungmin University, Department of Information and Communication
Includes the military service period
- Dec 2019 – Aug 2020
Bachelor's degree, Academic Credit Bank System (National Institute for Lifelong Education)
Degree conferred in Information and Communication
- Feb 2020 – Jul 2020
KG ITBANK: AWS Architecture Design Specialist Training Program
6 months, 800 hours. Project: migrating a fictional client to AWS
- Dec 2016 – Sep 2018
Military service (Republic of Korea Army, honorably discharged)
Sergeant. Signal soldier (switchboard operator)
From operations
to structure.
Looking for a team to join in a cloud infrastructure or security role. I turn infrastructure and security that relied on people's memory into structures that code protects.