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Hann .

Public Cloud Infrastructure & Security Engineer

Hi, I'm
Kim JunHyun

Kim JunHyun (Hann)

I turn infrastructure and security that people had to remember into systems that hold on their own.

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Portrait of Kim JunHyun
2020 ~
start of cloud career
4
clouds operated
3,500 +
servers operated at peak
20 +
service projects
15
certifications earned

Short Profile

Short profile

From live games to finance, I have designed and run cloud infrastructure at scale

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. Moving to Terragrunt cut deployment time by 40%. CSPM (cloud security posture checks) remediation rose from 60% to 85% or higher.

I started at an Azure managed service provider, led multi-cloud infrastructure for a game company, then moved security infrastructure into code at a financial IT organization. My favorite work takes a problem out of human attention and makes the safe option the default in code and pipelines.

At a glance

Name
Kim JunHyun
Location
Seoul, South Korea
Military service
Republic of Korea Army, honorably discharged
Education
Bachelor's, Information and Communications

Key technology

Tech
Stack

Terraform, Terragrunt, AWS, GCP, Azure, Tencent Cloud, Python, PowerShell, Bash, GitLab CI/CD, Jenkins, Zabbix, Grafana, Splunk, Docker

Regions I have run

Certifications

  • NCP Professional
  • NCA
  • Engineer Information Processing
  • AZ-900
  • +11

6 active · 9 in history

Have a question?

Kim JunHyun holding a pet dog

From real repository code

Infrastructure as Code,
Security by Default

Five things I do well

Choose a card to see only the projects in that area

My Experience

Feb 2026 – Oct 2026

Woori FIS

Woori FIS

Network Security Team, Information Security Department

Assistant Manager · Cloud Security Engineer

Designed, built, and operated cloud security architecture for affiliates including Woori Bank, Woori Card, and Woori Financial Group, across a hybrid environment of public cloud, private cloud, and on-premises.

  • Brought AWS Network Firewall, WAF, and Shield security infrastructure under code for the first time, in an environment with no Terraform
  • Built a Python pipeline that automatically collects and analyzes network communication settings across multiple AWS accounts
  • Integrated GuardDuty, Security Hub, WAF, Network Firewall, and Shield with a Splunk-based SIEM/SOAR
  • Defined IAM permissions in Terraform to block excessive grants by design, following Zero Trust principles and the network separation (a Korean financial regulation) requirements in Korea's Electronic Financial Supervisory Regulations
  • Operated hybrid security solutions together: FortiGate, NxPortrait, and WIPS
  • Helped set security policy as an early member of public cloud adoption in the financial sector

Feb 2023 – Feb 2026

Com2us Platform

Com2us Platform

Infrastructure Technology Team C, Infrastructure Technology Office, Cloud Division

Assistant Manager · Cloud Engineer

Main engineer in charge of design, build, operations, and incident response for multi-cloud game service infrastructure across 4 cloud service providers (CSPs): AWS, GCP, Azure, and Tencent.

  • Cut deployment time by 40% by moving from Terraform to Terragrunt
  • Migrated from GCP to Tencent Cloud with zero downtime (80 servers and 20 databases, completed within one week)
  • Raised CSPM (cloud security posture check) remediation from 60% to 85% or higher
  • Cut DragonSky infrastructure costs by up to 62%
  • Analyzed every cross-cloud firewall policy across Tencent and GCP, at 600 servers and 70 databases, then redesigned them
  • Automated audits in Python that collect assets and audit logs from 4 CSPs into a common schema. Permission grants, Access Key issuance, and changes to key servers and databases trigger immediate Slack and Telegram alerts
  • Handled audits across 4 CSPs with no security team working directly in the cloud: moved recurring findings into Terraform module defaults and mandatory validate and plan gates in CI/CD
  • Ran unified alerting with Zabbix, Grafana, Slack, and Telegram, and DDoS defense with GCP Cloud Armor

Aug 2020 – Feb 2023

C&Thoth

C&Thoth

Cloud Service Team

Associate to Assistant Manager · Cloud Engineer (Azure MSP)

Main engineer dedicated to game company clients at an Azure managed service provider (MSP), covering design, build, operations, security audits, and deployment automation.

  • Dedicated operations for MIR4 Global game infrastructure: 3,500 servers and 650 databases worldwide
  • Automated DDoS detection and blocking with Azure Log Analytics and PowerShell
  • Improved deployment speed by 80% with PowerShell deployment automation (MIR4 Korea)
  • High-availability architecture on Dedicated Host, and real-time incident response
  • Built real-time dashboards with Telegraf, InfluxDB, and Grafana (TIG stack)
  • Handled client cloud security audits based on CSPM and ISMS (Korea's information security management certification)

Proof in code

The real structure of my public repositories, shown in motion

16 provider aliases, one assume_roleus-west-2us-west-1us-east-2us-east-1sa-east-1ap-south-1ap-southeast-1ap-southeast-2ap-northeast-3ap-northeast-2ap-northeast-1eu-north-1eu-west-1eu-west-2eu-west-3eu-central-1assume_roleSame role_arn in every region16 regions · 24 modules · one locals map per region

PF-01 · AWS · IaC

AWS multi-region Terraform

A Terraform module set that builds the same infrastructure in 16 AWS regions from one locals map per region.

Role
Design and implementation
Period
Personal project · released Nov 2026
Cloud
AWS
Scale
16 regions · 24 modules · 3 examples
Key tech
Terraform · AWS · EKS · CloudWatch
Case study GitHub
GKE node pool SURGE upgrademax_surge = 5 max_unavailable = 0New nodesOld nodesOld nodes leave one at a time · 0 unavailableSwapped to 5 new nodes · 0 nodes unavailableSoak 3600s applies only to BLUE_GREEN

PF-02 · GCP · IaC

GCP Terraform GKE platform

A module set that keeps capacity during GKE node pool upgrades with SURGE, and opens only what a VPN needs through a firewall baseline, all as code.

Role
Design and implementation
Period
Personal project · released Nov 2026
Cloud
GCP
Scale
22 modules · 3 examples
Key tech
Terraform · GCP · GKE · Cloud Logging
Case study GitHub
CloudAudit tracks into a COS bucketCOS bucketCAMCVMCBSVPCcam/cvm/disk/vpc/AddUserCreateApiKeyAttachUserPolicyRunInstancesTerminateInstancesResizeDiskCreateSecurityGroupPolicies4 audit tracks · one COS prefix per serviceRed border: risky event

PF-03 · Tencent · IaC

Tencent Cloud audit-ready Terraform

Tencent Cloud modules that define CloudAudit tracks per service, so risky changes land in a COS bucket.

Role
Design and implementation
Period
Personal project · released Nov 2026
Cloud
Tencent
Scale
18 modules · 3 examples
Key tech
Terraform · Tencent Cloud · CloudAudit · COS
Case study GitHub
iam_custom_policyiam_useriam_custom_roleiam_groupvpcelastic_ipebsinternet_gatewaysecurity_groupvpc_endpointvpc_peeringelasticache_subnet_groupnat_gatewayroute_tableinstance_profileec2_instance

PF-04 · AWS · Terragrunt

AWS Terragrunt DRY IaC

Sixteen Terraform modules behind one root config, with Terragrunt running them in order from their dependency graph.

Role
Design and implementation
Period
Personal project · released Nov 2026
Cloud
AWS
Scale
16 modules · 16 units · 4 dependency levels
Key tech
Terragrunt · Terraform · AWS
Case study GitHub
AWSGCPTencentCross-account roleiamfirewallinstanceloadbalancervpcaudit_logunusedCommon schemaGoogle SheetsSlackTelegramImmediate alerts on critical eventsMonthly archive

PF-05 · Multi-cloud · Python

Multi-cloud asset and audit automation

A Python tool that collects assets, permissions, and audit logs from AWS, GCP, and Tencent Cloud into one schema, and alerts on risky events.

Role
Design and implementation
Period
Personal project · released Nov 2026
Cloud
AWS · GCP · Tencent
Scale
3 clouds · 7 collectors · 49 audit actions
Key tech
Python · boto3 · Google Cloud SDK · Tencent Cloud SDK
Case study GitHub
CEOUser directiveManagementTechnologySalesEmmaChief of staffMiaFinanceAvaHRSophiaTech leadNoahSenior engineerLunaEngineerEthanDB engineerLiamQA engineerChloeSecurity engineerJamesPlanning and salesleadOliviaContent marketer(off by default)Model priority · estimated cost recordedSimulated: assignment, model selection, and cost tracking onlyNo language model API is called

PF-06 · AI · FastAPI

AetherCrew: a virtual company of 11 AI employees

A hand-built orchestrator that assigns work, picks models, and tracks cost for 11 AI employees in a virtual company. Agent work is simulated and no language model API is called.

Role
Design and implementation
Period
Personal project · released Nov 2026
Cloud
None
Scale
11 AI employees · 3 divisions · 8 dashboard pages
Key tech
Python · FastAPI · WebSocket · pytest
Case study GitHub
Firewall requestSource · Destination · Portnetops confirmnetops modifynetops flowlogIs it already open?Preview only the blocked flowsVerify with real trafficOpenNo work neededBlockedOn to the next stepPreviewPrints affected resources andrules--apply + typed applyAdds rules onlyTraffic foundCloudWatch Logs · AthenaNothing changes by default

PF-09 · AWS · Python

AWS firewall request automation

A CLI that checks whether a firewall request is already open, previews changes only for what is blocked, and verifies the real traffic.

Role
Design and implementation
Period
Personal project · released Nov 2026
Cloud
AWS
Scale
3-step CLI · 4 input formats · 4 resource types
Key tech
Python · boto3 · AWS · CloudWatch Logs
Case study GitHub
See all case studies

Results at work

The services I ran at each company, and what changed

Woori FIS · AWS · Security

IaC 0 → Terraform

Network Firewall and WAF standardized in code

Woori Financial Group AWS security architecture

Role
Cloud Security Engineer · Network Security team, Information Security
Period
Feb 2026 – Oct 2026
Cloud
AWS
Scale
Multiple AWS accounts
Key tech
Terraform · AWS Network Firewall · AWS WAF · AWS Shield Standard

Case study

Com2us Platform · Migration

About 1 week

Zero downtime, 80 servers and 20 databases

Zero-downtime migration from GCP to Tencent Cloud

Role
Cloud Engineer · Main engineer
Period
Feb 2023 – Feb 2026
Cloud
GCP · Tencent
Scale
80 servers · 20 databases
Key tech
Terraform · GCP · Tencent Cloud · Online Migration

Case study

Com2us Platform · Multi-cloud

600 / 70

Servers / databases, GCP and Tencent multi-cloud

Summoners War: Sky Arena multi-cloud and firewall redesign

Role
Cloud Engineer · Main engineer
Period
Feb 2023 – Feb 2026
Cloud
GCP · Tencent
Scale
600 servers · 70 databases · Massive
Key tech
GCP · Tencent Cloud · Terraform · Terragrunt

Case study

C&Thoth · Azure MSP

3,500 / 650

Servers / databases, global game on Azure

MIR4 Global: massive Azure infrastructure and automated DDoS blocking

Role
Cloud Engineer · Main engineer (client: WEMADE)
Period
Jul 2021 – Feb 2023
Cloud
Azure
Scale
3,500 servers · 650 databases · Massive
Key tech
Azure · Dedicated Host · PowerShell · Log Analytics

Case study

Com2us Platform · FinOps

Up to -62%

Infrastructure cost

Dragon Sky FinOps: 62% lower infrastructure cost

Role
Cloud Engineer · Main engineer
Period
Feb 2023 – Feb 2026
Cloud
Azure
Scale
10 servers · 5 databases
Key tech
Azure · Python · Billing monitoring

Case study

CSP 15 projects

Also worked on: Birdie Crush: Fantasy Golf · Wannabe Challenge · Soccer Spirits

Problems I met, and how I decided

What I found, how I judged it, and how I fixed it, shown scene by scene

03:00Office lights outGame serviceMitigation flow logsSources with abnormal SYN volumeNSG block rules203.0.113.x203.0.113.x203.0.113.xNo one stepped in. The service kept running.

C&Thoth · Aug 2020 – Feb 2023

Stopping 3 a.m. DDoS attacks with no one on the keyboard

Detect → block automated0 human steps

One month?????????????????????????????ReviewAWSCloudTrailGCPCloud Audit LogsAzureActivity LogTencent CloudCloudAudit●●●●▲▲▲▲■■■■★★★★NormalizeWho · When · Where · WhatAWS · game-a-prod · Access Key issuedGCP · game-b-live · Project role addedTencent · game-c-cn · Security group rule addedAzure · tool-rg · Server createdResolvedResolvedSlackTelegramAutomatic review every day before dawnMonthly → Daily

Com2us Platform · Feb 2023 – Feb 2026

From a monthly security review to a daily automatic one

Monthly → Daily4 Clouds

LIVEGCPTencent CloudFirewall rules firstOnline Migration · 80 server blocksPrivate validationTraffic cut overAbout 1 week · 0 downtimegcp.tf → tencentcloud.tf

Com2us Platform · Feb 2023 – Feb 2026

Moving a live game between clouds without stopping it

1 Week0 Downtime80 Servers / 20 DBs

DMZ subnetPrivate subnetRegulationSeparate the DMZNo public IPsApproved exits onlyWallLocked doorNarrow exitOne codebase, every accountTerraform codeAccount AAccount BAccount C…New accounts get the same security baseline

Woori FIS · Feb 2026 – Oct 2026

Setting a security baseline for a financial cloud that had none

IaC 0 → Terraform standard

See all field notes

Certifications

Expired certifications are listed as history

My Journey

  1. 2013

    Volunteer work in Nepal

    Joined "Precious Wings 2" (Seoul Metropolitan Mangwoo Youth Center) and helped with a local school sports day and facility improvements.

  2. 2015

    Enrolled at Kyungmin University, Information and Communication

    Started learning networks and servers.

  3. 2016–2018

    Military service (Republic of Korea Army, honorably discharged)

    Served as a signal soldier (switchboard operator) and was discharged as a sergeant.

  4. 2020

    Completed AWS training and earned a degree

    Migrated a fictional client to AWS in KG ITBANK's 800-hour course, and earned a bachelor's degree through the Academic Credit Bank System.

  5. 2020

    Joined C&Thoth

    Started my career as an Azure MSP engineer, operating MIR4 Korea, ADT-CAPS, and others.

  6. 2021

    Main engineer for MIR4 Global

    Owned the largest infrastructure I have worked on, 3,500 servers and 650 databases, from early design onward.

  7. 2023

    Joined Com2us Platform

    Began operating 4 clouds together: AWS, GCP, Azure, and Tencent.

  8. 2024

    Terragrunt adoption and Tencent migration

    Hit Terraform's limits running many regions at scale, so I changed the structure. Moved clouds with no service interruption.

  9. 2026

    Woori FIS, Information Security Department

    Moved to the financial sector and brought security infrastructure code to an environment with no Terraform.

  10. 2026.11

    Next challenge

    Looking for a team to join in a cloud infrastructure or security role.

Let's talk

I am looking for a cloud infrastructure or security role. Questions are welcome.

Send an email

kimjhtlzk@naver.com +82 10-9092-0615

My notes on infrastructure fundamentals are on my tech blog, across 50 posts.

Open to work · Cloud infrastructure and security