System online // Operator

Hey there. I'm Daniel.

//

I go by a few aliases, and "jooncco" is the one I use when I build things. I started out as a back-end engineer at LG CNS and grew into a full-stack engineer any team would love to work with. I've led business-critical projects of every size to the finish line — scroll down for the mission log.

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Solutions Architect
Full Stack Engineer
AI Agent Builder
Algorithmic Trading Enthusiast
Mission log

Projects

Legacy EC2 → EKS Migration

Jan 2026 – Jun 2026

★

▸ Led the EC2-to-EKS migration of 8 legacy systems (work portal, search engine, official homepage, and more).

  • Led the EC2-to-EKS migration of 8 legacy systems (work portal, search engine, official homepage, etc.).
  • Designed K8s resources (PV, ConfigMap, Secret) and implemented Helm charts.
  • Coordinated OS upgrades and re-installation for 4 systems across teams.
  • Designed and ran per-system availability and performance test cases.
  • Wrote operations guides and ran developer onboarding.
Amazon EKSKubernetesHelmDockerAmazon EC2

Automated Feedback Notification System

Dec 2023

★

▸ Architected an anomaly-detection pipeline that scrapes KakaoTalk feedback, scores sentiment, and automatically alerts the responsible team.

  • Owned the overall system design.
  • Built the Scrapper — a Python app that automates export of KakaoTalk chat content.
  • Built the Uploader — a Spring Boot app that parses chat text and uploads it to S3.
Amazon EC2AWS LambdaAmazon S3Amazon RDSAmazon ComprehendAmazon SESPythonOpenCVSpring Boot

UCMP — Cloud Resource Management Platform

Jul 2021 – Feb 2022

▸ Built a platform to provision standardized GCP/AWS resources and projects in a few clicks, with email 2FA and notifications.

  • Implemented email-based two-factor authentication.
  • Built the sign-up / sign-out pages and their REST APIs.
  • Built the cloud-resource creation page and its REST APIs.
  • Added email notifications via Amazon SES.
Spring BootMyBatisThymeleafReactMySQLAWSGitHub API

Fast Download for TB-scale Files

Jan 2024 – Feb 2024

▸ Cut download time for a 1.2 TB file by 40% with a custom multipart download module in a Next.js app.

  • Designed and implemented a multipart download module with Axios.
  • Built the front-end app with Next.js and Tailwind CSS.
Next.js 14Tailwind CSSZustandAxiosAmazon S3

IPTV Web Application Modernization

Feb 2023 – Nov 2023

▸ Modernized next-generation IPTV web servers and halved a device-initialization API's latency with executor threads.

  • Implemented REST APIs for IPTV device authentication and initialization from device metadata.
  • Reduced a device-initialization API's execution time by 50% using executor threads.
  • Built a batch microservice that periodically ships log files to S3 for monitoring.
Spring BootMyBatisMySQLAWS

NFT Marketplace "Naemo World"

Mar 2022 – Dec 2022

★

▸ Shipped wallet, social OAuth, and launchpad features for an NFT marketplace serving creators and collectors.

  • Built the My Wallet page and related REST APIs (wallet connect, balances, etc.).
  • Implemented SNS OAuth (Twitter, Discord, Telegram, Instagram).
  • Built the SNS event mission page and Ethereum/Solana withdraw APIs.
  • Built the admin Launchpad list page and its REST APIs.
Spring BootSpring Data JPAQueryDSLMySQLReactMobXAWS
naemo.io ↗

Life-Insurance Point Platform "P3"

Feb 2021 – Jun 2021

▸ Delivered blockchain-ledger-backed point transactions (payment, transfer, refund) for a life-insurance rewards platform.

  • Built point-transaction REST APIs: payment, transfer, refund.
  • Built the admin point-usage history page and its REST APIs.
Spring BootMyBatisReactMySQLAWS

"Okimoki" — Coffee Order Chatbot

Jan 2020 – Dec 2020

▸ Designed and built three backend microservices (store, menu, order) powering coffee ordering inside KakaoTalk.

  • Designed and implemented three back-end microservices: store, menu, order.
  • Modeled coffee-coupon data.
  • Designed and implemented two-factor authentication.
Spring BootSpring Data JPASpring WebFluxPostgreSQLAWS

Airline VoC GenAI Backend

Jul 2025 – Dec 2025

★

▸ Built the GenAI backend that processes airline Voice-of-Customer in the background — classification, summarization, translation, similar-VoC lookup, and keyword extraction.

  • Built background VoC-processing APIs: classification, summarization, translation, similar-VoC lookup, keyword extraction.
  • Designed the backend interface and data model, and integrated Amazon Bedrock.
  • Achieved 95%+ classification accuracy and 94%+ retrieval accuracy.
Amazon BedrockGenAISpring BootJava

OCR Meter Reading Application

Aug 2024 – Jun 2025

★

▸ Led a successful PoC for an image-based intelligent electricity-meter reading app — from architecture through production Flutter delivery.

  • Designed the prototype web-app architecture and drove the PoC to sign-off.
  • Built the React front end and a serverless backend on AWS Lambda.
  • Shipped the production Flutter mobile application.
React 18AWS LambdaAmazon EC2Amazon TextractYOLOv9OCRFlutter

GenAI Audit Assistant Bot

Mar 2024 – Jul 2024

★

▸ Delivered a Claude 3.5 Sonnet RAG assistant that augments regular audits with bilingual (KO/EN) knowledge retrieval.

  • Customized the AWS Bedrock RAG sample (bedrock-claude-chat) for the audit workflow.
  • Prompt-engineered multi-language (Korean, English) knowledge augmentation.
  • Wrote the AWS Lambda trigger for knowledge-base sync workloads.
Amazon BedrockAmazon S3AWS LambdaGenAIClaudeAWS CDK

Bitcoin Price Predictor Research

Jul 2018

▸ Exploring systematic crypto strategies — LSTM/regression model based, with ledger data.

  • Built market-indicator + Google-Trend feature pipelines for price prediction.
  • Prototyped regression and LSTM RNN forecasting models.
  • Backtests trading signals against historical OHLCV data.
PythonLSTMPandasNumPyBacktesting
Reactor clusters

Skills

JavaSpringSpring BootQueryDSL JPAMyBatisFlywayMySQLPostgreSQLAWS LambdaAmazon API GatewayAmazon RDS
Hangar bay

Portfolio

Spring Boot API Server Template

Spring Boot API Server Template

Production-grade Spring Boot REST API starter — example endpoints for a fast productivity boost.

blog.me

blog.me

This portfolio, built with Next.js + Tailwind. Fork it for your own developer portfolio.

jooncco.github.io

jooncco.github.io

A dev blog on GitHub Pages using the Jekyll “Minimal Mistakes” template.

Bitcoin Price Predictor

Bitcoin Price Predictor

Bitcoin price prediction from market indicators and Google Trends using regression models and an LSTM RNN.

Coindrop Game AI Agent

Coindrop Game AI Agent

A reflex agent trained with reinforcement learning (Q-learning) that plays a pygame coin-drop game.

“is-a” Relationship Teller

“is-a” Relationship Teller

NLP for Korean words — tells whether an {Entity, Concept} pair holds an “is-a” relationship.

KakaoTalk Chat Exporter

KakaoTalk Chat Exporter

An OpenCV macro that periodically exports the contents of a KakaoTalk chat room.

CP Snippet Java

CP Snippet Java

A JSON config of Java code snippets — extremely handy for competitive programming.

CP Stamper C++

CP Stamper C++

A simple comment writer that stamps generated comments with author and timestamp.

Problem solving

Competitive Programming

LeetCode

@jooncco

Live

Tier: Knight

1,977
Rating
24,675#
Global rank
22
Contests
2.92%
Top
View profile ↗

Codeforces

@jooncco

Live

Tier: pupil

1,255
Rating
17,369#
Global rank
47
Contests
2.77%
Top
View profile ↗
Service record

Experience

  1. Solutions Architect

    2026.01 – 2026.06

    Led the EC2-to-EKS migration of 8 legacy systems.

    • Designed K8s resources (PV, ConfigMap, Secret) and Helm charts.
    • Ran per-system availability/performance tests and led developer onboarding sessions.

  2. AI Backend Engineer

    2025.07 – 2025.12

    Built the GenAI backend that processes airline VoC in the background.

    • Built VoC APIs: classification, summarization, translation, similar-VoC lookup, keyword extraction.
    • Integrated Amazon Bedrock; reached 95%+ classification and 94%+ retrieval accuracy.

  3. Prototyping Engineer

    2024.08 – 2025.06

    Prototyping and productionizing an image-based intelligent meter-reading app.

    • Designed the PoC architecture and led it to sign-off.
    • Built the React front end and an AWS Lambda serverless backend.
    • Shipped the production Flutter application.
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