— Portfolio · 2025

Byeonghee Oh

Cross-Platform Developer · RAG Engineer

  • User experience first
  • Built and operated web, serverless web, and mobile services
  • Shipped on-device RAG engine (Rust FFI · ONNX) on pub.dev
  • Improved bottlenecks in complex data pipelines
  • Structure-first engineering for stable services
5 years 4 months total · 3 years Web · 4 years Mobile
— Languages
TypeScriptDartPythonRustKotlin
— Mobile
FlutterJetpack ComposeReact Native
— Web
ReactNext.jsVue · Nuxt
— Backend · AI
FastAPIPostgreSQLMilvusSBERTONNX RuntimeDocker

Open Source Packages

pub.dev

High-performance Flutter packages I developed and published on pub.dev

🚀

mobile_rag_engine

v0.18.5
  • ·100% on-device — fully offline semantic search
  • ·Hybrid retrieval — HNSW dense + BM25 sparse
  • ·PDF · DOCX ingestion via fast-path file API
  • ·Zero-copy embedding transport over Rust core
RustFlutter FFIONNX RuntimeHNSWBM25SQLite
⚙️

rag_engine_flutter

v0.18.3
  • ·Native Rust FFI via flutter_rust_bridge
  • ·10–100× faster tokenization than pure Dart
  • ·HuggingFace Tokenizers (BPE · WordPiece) compatible
  • ·iOS · Android · Desktop packaging via cargokit
Rustflutter_rust_bridgecargokitHuggingFace Tokenizers

Selected Work

08 Projects
01
WEB

Swifty-law

In-house engine that normalizes official Korean statute data into citable chunks and serves hybrid retrieval so LLMs answer only within official sources with full citations.

Core Stack

PythonFastAPIPostgreSQLMilvus+2

Built Bronze/Silver/Gold three-tier lake so chunks and embeddings can be regenerated from raw API at any time.

02
APP

Easy Contract Viewer

A Flutter app that imports insurance PDF contracts, indexes clauses locally with mobile_rag_engine, surfaces review priorities, and opens the exact source PDF highlights with optional AI summaries.

Core Stack

FlutterDartRiverpodGoRouter+2

Built PDF ingestion and clause-aware chunking with pdfrx while preserving page rectangles for source highlights.

03
TABLET

FIET Fitness Trainer

A trainer-only app for FIET Fitness Center. Provides member management, workout program design, diet management, and weight data tracking in a tablet-optimized interface.

Core Stack

FlutterDartFirebase

Built tablet-first Flutter UI and reusable widgets for trainer workflows.

04
APP

FIET Fitness

A fitness center app by an AI health company. Syncs with trainers to view customized workout programs and diet plans, and tracks progress.

Core Stack

FlutterDartFirebase

Implemented workout and diet tracking screens with Flutter state-driven UI.

05
APP

Local Mobile RAG Gemma

Released v0.18.5

Implemented a mobile RAG engine that runs fast on local devices and released it through v0.18.5. Uses Gemma 3n to store models locally and provides answers to user questions.

Core Stack

FlutterRustONNX RuntimeSQLite+2

Connected Flutter and Rust through FFI for on-device RAG orchestration.

06
WEB

Motgo Restaurant Voting

A web service that automatically fetches restaurant info from Naver Map URLs, allowing friends to vote together. Provides real-time voting status and result analysis.

Core Stack

Next.jsTypeScriptTailwind CSSPostgreSQL+2

Built real-time voting flow with Next.js and TypeScript plus shareable links.

07
APP

HaruCheck

A health management app that records daily workout/diet certifications and provides AI weekly reports using Google VertexAI (Gemini). Supports calendar-based tracking and interactive data visualization.

Core Stack

FlutterFirebaseFirestoreVertexAI+2

Built certification tracking UX with Flutter and Riverpod state architecture.

08
APP

Weedool (TuringBio)

A digital therapy-oriented service using Behavioral Activation (BA) techniques. Provides emotion selection, BA recommendations, status monitoring, and counseling center information.

Core Stack

FlutterRiverpodGoRouterNaver Map API+1

Implemented counseling and activity flows with Flutter, Riverpod, and GoRouter.