Mouton Journal
Private diary with a cute AI companion.
A subscription-based commercial iOS app (actively developed until April 2025). I built everything from ideation to planning, design, and back-office tools entirely on my own. Available in 8 languages: English, German, Korean, Japanese, Chinese, French, Italian, and Spanish.
Key Features
- AI Companion that likes your posts and writes empathetic comments on your diary entries
- Clean, social media-inspired design
- Calendar view and search functionality
- Optimized for iPhone and iPad, also runs on macOS (Apple Silicon)
- Support for comments and quote-sharing
- PDF export
Jan 2025
Mar 2025
1,653
Flutter, Django
Technical Details
๐๏ธ Offline-First Architecture
All journal entries are stored locally using SQLite with FTS5 (Full-Text Search) for instant search capabilities. Data syncs to the server when online with sophisticated conflict resolution and change tracking.
๐ค AI-Powered Interactions
Mouton's personality is powered by OpenAI's GPT models with custom prompt engineering. Includes content moderation, emotion matching, and multi-language support. Comments are generated contextually based on entry content and attached images.
๐ฆ Rust Integration
Performance-critical operations like image resizing are handled by Rust modules viaflutter_rust_bridge. Uses the fast_image_resize crate for efficient image processing, ensuring smooth performance even with multiple high-resolution photos.
๐ Smart Synchronization
Implements a sophisticated sync protocol with change tokens, automatic conflict resolution, and retry logic. Supports offline post creation with automatic sync when reconnected.
๐ Rich Content Support
Automatic link preview generation with OpenGraph parsing, special YouTube handling, and support for quoting other entries or comments in a social media-style interface.
iOS Apps built in Collaboration
9 side projects created with designer Eui-Hyung Jung (2015-2023)
Sole developer on all projects (Swift, Objective-C, Flutter)
Daygram
E-ink Style Simple Diary with Password
Minimal diary app designed to capture thoughts and feelings with intuitive interface. Features password protection and cloud sync.
Flink
Bullet Notes / MinimalList TODO
Ultimate tool for schedule management and to-do list organization with sleek design and e-ink style interface.
Otter
Easy Calorie Counter
Simple food diary app to track daily calories with minimalist design and easy food entry system.
Tables
Designed for Simple Scheduling
Grid-based planner app for organizing life with customizable layouts and visual task management.
Fews
Well begun is half done
Build habits with minimal friction. Simple habit tracker focused on getting started rather than complex systems.
Kipkam
Take a deep breath
Breathing exercise app with visual guides and calming animations for stress relief and mindfulness.
CampNight
Nature sounds for better sleep
Natural sleep sounds app featuring campfire, rain, and nature ambience for better sleep quality.
Haru
Have a good day!
Elegant calendar app with memo features combining scheduling and note-taking in minimalist design.
Tabatach
Interval workout timer
Tabata interval training timer with customizable workouts and visual progress tracking for fitness enthusiasts.
Work Experience
Product Owner & Engineer
Architected and launched Mouton Journal, a personal diary app with AI-powered features. Integrated LLM capabilities for intelligent comments, achieving 1,600+ commits in 5 months.
Senior Software Engineer
Architected RESTful APIs for Japanese e-commerce platform nugu.jp. Used Next.js, Svelte, Django. Mentored team on Django best practices.
Chief Technology Officer
Achieved 75% AWS cost reduction through strategic optimization. Led technical architecture using Django, React, and PostgreSQL.
Chief Technology Officer
Launched K-POP fandom app with Flutter reaching 10K+ users. Engineered real-time video broadcasting with WebRTC and FFmpeg/CUDA optimization.
Senior Software Engineer
Architected AI-powered chatbot engine for Kakao's smart speaker. Ported KakaoTalk messenger server from Linux to macOS for faster local development.
Chief Technology Officer
Co-founded company, developed iOS app with Swift and Flask backend. Led team of 2 junior engineers to deliver in 4 months.
Senior Software Engineer
Designed UI test automation for "Need for Speed Edge". Reduced QA testing time by automated test suite implementation using customized PhantomJS.
Senior Software Engineer
Developed social music player Android application. Maintained Python API server handling 1M+ daily requests.
Senior Software Engineer
Reduced AWS costs by $200,000/month through infrastructure optimization. Maintained Android App. Enhanced Django app for 10M+ daily requests.
Professional Consultant
Prototyped comment plugin backend using Node.js. Implemented Platform-as-a-Service solution based on CloudFoundry. Developed custom Nginx extension using C/GLib.
Independent Software Engineer
Developed MSN Messenger clone for Android with 2M+ downloads, generating $100K+ revenue through Google Ads.
Software Engineer
Developed MSN Messenger bot for SpringNote. Implemented secure private messaging service with OpenID authentication.
Early Career
Started at CyberImagination (1999), progressed through roles at Linux Korea, and Tri-D Communication. Used Java, C++, and Python.