pyrimidine

I build things so I can enjoy what I love more deeply.

I write server code and play guitar in AiBO!!!!!, a MyGO!!!!! cover band. I also travel to see bands live.

About

When I get into something, I hold on to it for a long time. Sooner or later I find myself building something for it. A few of the services below started that way.

On this blog I write down what I fixed while running them, and why. Sometimes it's about the band. Posts are in Korean.

Lives in: Incheon
Studies: Computer Science, Inha University
Plays in: AiBO!!!!!, guitar

What I love

Guitar and the band
I play guitar in AiBO!!!!!, a band that covers MyGO!!!!! songs.
aibo.band
Live trips
I travel to see the bands I love play live. I started building oshi@log to keep a record of the shows and pilgrimage spots.
Railways
I like subways, which is how RailNetwork started. These days I work with Japanese railway data too.
Favorites
I love characters from BanG Dream!, Girls Band Cry, Bocchi the Rock!, THE IDOLM@STER, and Love Live!. My favorite voice actor is Hina Aoki.
gallery

Tools

Backend

Go, gRPC, Kotlin, Spring Boot 3, Spring Modulith, TypeScript, Node.js, Fastify, Python

Go for RailNetwork-JP, Kotlin and Spring for oshi@log, TypeScript for the RailNetwork server.

Data

PostgreSQL, PostGIS, MySQL, Redis, MongoDB

Location data lives in PostGIS, and live train state in Redis.

Infra & ops

Docker, Jenkins, Ansible, Cloudflare, Oracle Cloud, Tailscale, Prometheus, Grafana, Loki

My services run on Oracle Cloud servers and Cloudflare, and I handle deploys and monitoring myself.

App & web

Flutter, React, Next.js, Astro, Tailwind CSS

The RailNetwork app is Flutter. This site is Astro.

Algorithms & ML

C++, Python, PyTorch, TensorFlow Lite, scikit-learn

I taught algorithms in a campus club, and ran a TensorFlow Lite model on a tiny device during a research project.

Things I have built

RailNetwork
Running
Since 2023Backend and infra, with one other person
Shows where Seoul subway trains are right now.
TypeScript, Fastify, gRPC, MongoDB, Redis, Flutter
oshi@log
App in testing
Since 2025Backend, solo
A map-based log of the lives and pilgrimage spots band fans have been to.
Kotlin, Spring Boot 3, Spring Modulith, PostGIS, Redis
RailNetwork-JP
In progress
Since 2026Solo
Brings real-time train data from several Japanese rail operators into one API.
Go, gRPC, SSE, Redis, MySQL
Noraneko Platform
Running
Since 2026Solo
An ops platform that builds, deploys, and watches over my side projects.
Go, Jenkins, Ansible, Docker, Prometheus, Grafana

The road so far

2026
1. 07
  Started Noraneko Platform
2. 05
  Started RailNetwork-JP
2025
1. 08
  Started oshi@log
2024
1. 12
  Top prize, Carbon Neutral Innovation Academy
  I built the matching system for a shared taxi platform.
2. Completed Google's ML Bootcamp
  Fine-tuned Gemma 2 2B to recommend Baekjoon algorithm problems.
3. Competitions
  24th of 1,844 teams in Reply Code Challenge, 11th in the Dacon Inha AI Challenge, 83rd of 2,236 teams in Kaggle Insurance Cross Selling.
2023
1. Competitions
  5th in the campus AWS DeepRacer league, top 6 at the AWS·KT AICE Big Data & AI Competition, 3rd in the ICPC Seoul Regional campus qualifier.
2. 07
  Joined a portable ECG monitor research project
  Built a small arrhythmia detection model from ECG data and ran it on an Arduino.
3. 07
  Started RailNetwork
4. 02
  Started Computer Science at Inha University
  As an organizer of the IGRUS and CTP clubs, I taught C++ and Python problem solving to about 40 students.