Frontend Developer Who Also Designs AI Agent Harnesses 👋

Started as a blockchain (Solidity) developer and within 4 years led the framework migration and monorepo transition of a B2C mobile platform running 10 services, achieving an 88% AWS cost reduction (about $16,500 saved annually) and a 60% loading speed improvement.

🚀 Key Achievements

📊 Cost Optimization

• 88% total AWS cost reduction: $1,500+ → $120/month (about $16,500 saved annually)
  • Phase 1 migration (SSR → CSR): 65% reduction
  • Phase 2 CloudFront optimization: 76% additional reduction ($500 → $120/month)
• 90% fewer CloudFront requests: 12M → 1M requests/month
• 90% cache hit rate, initial loading speed improved 60% (3s → 1.2s)

🏗️ Architecture Design

• Led Nuxt.js → React migration: 10 core services, 10 months, 2-person team
• Built a monorepo: PNPM workspace + Turborepo cut CI build time by 80%
• Lambda@Edge + S3 progressive deployment: page-level independent deployment pipelines

🛠 Operations & Automation

• Resolved Bluetooth IoT failures: connection failure rate down 80%, customer inquiries down 90%
• Automated development processes: 70% less time on locale packs, 90% less on terms updates
• Operated an AI agent harness: caught critical bugs in a 150-file, 8,000-line PR before review

💼 Career

Frontend Developer

September 2022 ~ Present

Led technology transformation and optimization while operating 10 independent services at a campus-focused B2C mobile app company.

1. Led the Nuxt.js → React Migration Project

Jan 2025 ~ Nov 2025 (10 months)

• Progressively migrated 10 core services (main, charging, conversion, laundry, point, ticket, etc.)
• Designed a progressive deployment strategy based on Lambda@Edge + S3
• Served as lead of a 2-person team

Technical Decisions

• Chose Context API + React Query over Redux
• Chose Vite as the bundler (10x faster HMR than Webpack)
• Chose Lambda@Edge for its low operating cost

✅ Result: 65% AWS cost reduction in phase 1, lower maintenance cost

2. Built the Monorepo Architecture

• Built an integrated multi-service management system on PNPM workspace
• Designed shared UI libraries (packages/ui, packages/styles, packages/utils)
• Configured independent build/deployment pipelines per page
• Introduced Turborepo build caching

✅ Result: 80% shorter CI build time (full rebuild → only changed apps), 35% shorter deployment time, 25% smaller bundle size

3. CloudFront Cache Optimization and Cost Reduction

Jan 2025 ~ Nov 2025

• Segmented CloudFront caching policies (separate strategies for HTML/CSS/JS)
• Optimized S3 static file compression (Brotli + Gzip) and CDN configuration
• Implemented dynamic routing with Lambda@Edge

✅ Result

• CloudFront cost down 76% ($500 → $120/month)
• Total AWS cost down 88% ($1,500+ → $120/month, about $16,500 saved annually)
  • Phase 1 (migration): 65% reduction via SSR → CSR
  • Phase 2 (optimization): 76% additional reduction via CloudFront tuning
• CloudFront requests down 90% (12M → 1M/month)
• Loading speed improved 60% (3s → 1.2s), 90% cache hit rate

4. Bluetooth IoT Incident Response and Monitoring System

Apr 2025 ~ Jun 2025

• Debugged washing machine Bluetooth connection failures for 2 months (40~50+ cases per day on average)
• Proposed and implemented Sentry error tracking
• Designed a detailed log collection structure in collaboration with app developers
• Analyzed error patterns → confirmed occurrence only on specific devices/OS versions → added timeout and retry logic

✅ Result: 65% faster incident response (2 hours → 40 minutes on average), 80% lower connection failure rate, 90% fewer customer inquiries

5. Development Process Automation

Jul 2023 ~ Aug 2024 (13 months)

Semi-automated locale pack system

• Planners manage Korean/English translations in MS Excel → developers run a terminal command
• Node.js script converts Excel → JSON automatically
• Tech: Node.js, xlsx library, custom JSON conversion logic

Terms update automation

• Built a Notion → HTML automatic conversion system
• Script applies service CSS to the generated HTML automatically

✅ Result: 70% less time for locale pack updates, 90% less time for terms updates (30 minutes → 3 minutes), higher development productivity

6. Domain Service Development

• Charging/Payment: integrated multiple payment methods including gift certificates and virtual accounts
• Laundry: built a washing machine control system integrated with Bluemeter (Bluetooth IoT) and app-web bridge communication
• Games: built real-time ranking systems for roulette and jump games
• Ticketing: built a musical/performance booking platform integrated with Clip

7. Design System and Collaboration Culture

• Built a Figma design token system (style-dictionary)
• Introduced Storybook → documented design tokens and key components
• Proposed and ran weekly technical sharing sessions

✅ Result: improved design-development collaboration efficiency

8. AI Agent Harness Design and Operation

• Authored project context documents: architecture, per-app domain responsibilities, shared package impact scope, agent behavior rules, and task completion checklists
• Designed agent constraint rules: no refactoring outside the requested scope, mandatory justification for new abstractions, explicit listing of affected apps when shared packages change — preventing review cost from unnecessary over-engineering
• Established per-task manual toggling for MCP (Sentry/Figma): limited always-connected servers to 2~4 to manage the token budget
• Built a GitHub PR review automation skill: Critical/Medium/Low severity classification, automatic summary and inline comments, review log storage and statistics

✅ Result

• Detected and fixed critical bugs that humans easily miss in a 150-file, 8,000-line PR through AI review
• Recorded and accumulated reasons for rejected review comments → built a system that keeps improving review standards so the same issues are not repeated
• Refined Sentry error data (removed noisy alerts, tagged user identifiers on core features) to narrow the investigation scope for root cause analysis

Tech Stack

React, TypeScript, Vite, React Query, Nuxt.js, Vue.js, PNPM workspace, Turborepo, AWS (Lambda@Edge, S3, CloudFront), Sentry, Storybook, style-dictionary, Node.js

Blockchain Developer & NFT Projects

June 2022 ~ September 2022 (3 months)

Through experience in Solidity-based smart contract development and NFT minting platform construction, I gained a deep understanding of blockchain technology and the Web3 ecosystem. I later transitioned to frontend development to deliver value to a broader user base.

Key Projects

• Delica NFT Minting Platform: Solidity smart contract design and React-based frontend implementation
• Bellygom NFT Project: Ethereum-based NFT issuance system development

Tech Stack: Solidity, Web3.js, Ethereum, React, ethers.js

💻 Tech Stack

Frontend

Monorepo & Build

DevOps & Tools

AI · MCP

Backend (Experience)

🎯 Strengths

1. Development Measured in Cost and Performance

I don’t stop at shipping features — I deliver measurable outcomes such as 88% AWS cost reduction, 90% fewer requests, and 60% faster loading.

2. Architecture Design and Technical Decision-Making

I design structures that fit the scale of the service — monorepos, progressive migrations, page-level independent deployment — and document why each choice was made.

3. Turning Repetitive Work into Systems

I convert manual, repetitive work such as locale pack updates, terms updates, and PR reviews into scripts and AI agent workflows.

4. Problem-Solving That Goes All the Way

For hard-to-reproduce problems like the 2-month Bluetooth communication issue, I rebuild the logging design itself to find the root cause.

📚 Tech Blog

Consistently documenting problems encountered in practice and their resolution processes.

AWS · Frontend

• CloudFront Cache Optimization: Read More
• CloudFront Cost Reduction: Read More
• Cookie Security Complete Guide: Read More
• React Query Usage Guide: Read More

MCP · AI Agent

I submitted Find Parking! to Kakao’s Agentic Player 10 competition. The MCP is publicly available on PlayMCP, and the preliminary application has been completed.

• Find Parking! Development Retrospective: Read More — Node.js MCP server, deployment to KC, and competition review
• Cursor MCP OAuth Authentication: Read More — Figma/Sentry login and token storage in Cursor
• MCP Series: Read More — From stdio/SSE to Remote MCP

👉 View Full Blog

📬 Contact

• Email: cjftns01@gmail.com
• GitHub: github.com/pocodingwer
• Blog: chuckplay.dev
• Instagram: @lim_cuck