Hi, I'm Jun.

I'm a Senior Cloud Infrastructure Engineer working across AWS and GCP, covering FinOps, SRE, and CI/CD. I've delivered 30-40% cloud cost reductions, report infrastructure work to the C-suite in business terms, and I'm the sole inventor of a 0-RTT VPN handshake (USPTO pending).

This site is where I keep my engineering notes (English and 日本語) and my resume.

About me

Resume: HTML · PDF · llms.txt

Articles

Claude Code faked its own work, then wrote me an unprompted confession
2026-07-13 · ai, llm, claudecode, agent, sre
I put a WAF on the front door. The spam wasn't using the front door.
2026-07-11 · security, cloudflare, waf, baas, frontend
Why did one day of AI cost more than a month of servers?
2026-06-29 · llm, claudecode, idempotency, ai
Claude Code detected a hack that never happened, then spiraled
2026-06-25 · ai, llm, sre, incident, monitoring
When should you publish a dev post? I counted, and JP vs EN are mirror images
2026-06-22 · blog, dataanalysis, devto, zenn, qiita
Playing hide-and-seek with an API key our CFO's Claude Code kept hiding
2026-06-18 · security, claudecode, secrets, ai
CPU and DB were bored, yet every site timed out: a slow-read bot that starved Apache's workers
2026-06-15 · apache, security, sre, ddos, monitoring
How a Slow Office VPN Led Me to File a US Patent
2026-06-08 · wireguard, vpn, cryptography, security, patent
Push a Docker Image to AWS ECR
2025-02-09 · aws, ecr, docker
Expose a Local Web Page with ngrok
2025-02-09 · ngrok, networking
Variables in Rust
2022-10-02 · rust
Create an ECS Fargate Service Step by Step
2022-08-22 · aws, ecs, fargate, docker, containers
React Context and useContext
2022-08-22 · react, hooks
React Effects and useEffect
2022-08-22 · react, hooks
React State and useState
2022-08-22 · react, hooks
Dockerizing a React App
2022-05-03 · docker, react
Pull the Nginx Image and Run the Container
2022-05-03 · docker, nginx, containers

Practice & drills (18)

Hi, I'm Jun.

Articles

Claude Code faked its own work, then wrote me an unprompted confession

I put a WAF on the front door. The spam wasn't using the front door.

Why did one day of AI cost more than a month of servers?

Claude Code detected a hack that never happened, then spiraled

When should you publish a dev post? I counted, and JP vs EN are mirror images

Playing hide-and-seek with an API key our CFO's Claude Code kept hiding

CPU and DB were bored, yet every site timed out: a slow-read bot that starved Apache's workers

How a Slow Office VPN Led Me to File a US Patent

Push a Docker Image to AWS ECR

Expose a Local Web Page with ngrok

Variables in Rust

Create an ECS Fargate Service Step by Step

React Context and useContext

React Effects and useEffect

React State and useState

Dockerizing a React App

Pull the Nginx Image and Run the Container

Dynamic Programming: Fibonacci Numbers

Dynamic Programming: 0/1 Knapsack Problem (1D & 2D DP)

Dynamic Programming: Longest Common Subsequence (LCS)

Dynamic Programming: Longest Increasing Subsequence (LIS)

Dynamic Programming

Segment Tree

Finding Perfect Numbers in Python

3. Longest Substring Without Repeating Characters

Greatest Common Divisor

Power

29. Divide Two Integers

26. Remove Duplicates from Sorted Array

1456. Maximum Number of Vowels in a Substring of Given Length

58. Length of Last Word

Binary Search

456. 132 Pattern

349. Intersection of Two Arrays

69. Sqrt(x)