Expense Tracking System — Full-Stack Data Application

Overview

A full-stack personal finance application for tracking, categorising, and analysing expenses in real time. Built with a three-tier architecture: Streamlit frontend, FastAPI REST backend, and MySQL database — demonstrating end-to-end software engineering beyond a typical data science notebook.

Key capabilities:

• Add, update, and delete expense records via an interactive UI
• Real-time analytics by category and monthly trends
• RESTful API with full unit and integration test coverage
• Persistent storage with a structured relational database schema

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Architecture

┌─────────────────────┐
│   Streamlit UI      │  ← Interactive frontend (Add/Update, Analytics)
└─────────┬───────────┘
          │ HTTP
          ▼
┌─────────────────────┐
│   FastAPI Server    │  ← REST API (CRUD endpoints, analytics routes)
└─────────┬───────────┘
          │ SQL
          ▼
┌─────────────────────┐
│   MySQL Database    │  ← Persistent storage (expenses, categories)
└─────────────────────┘

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Tech Stack

Layer	Technology	Purpose
Frontend	Streamlit	Interactive web UI
Backend	FastAPI	High-performance REST API
Database	MySQL	Relational data persistence
Testing	Postman + Unit Tests	API validation and DB coverage

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Project Structure

expense-tracking-system/
├── frontend/         → Streamlit UI pages and components
├── backend/          → FastAPI server and API endpoints
├── tests/            → Unit tests and integration tests
├── db_schema/        → Database schema and ER diagram
└── requirements.txt  → Python dependencies

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Setup & Running Locally

1. Clone and install dependencies

git clone https://github.com/Lua-Matlab-Python-R-J2EE/expense-tracking-system.git
cd expense-tracking-system
pip install -r requirements.txt

2. Start the FastAPI backend

cd backend
fastapi dev server.py
# API available at http://localhost:8000

3. Launch the Streamlit frontend

cd frontend
streamlit run app.py
# App available at http://localhost:8501

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Features & Status

Feature	Backend	Frontend	Tests
Add / Update Expenses	✅	✅	✅
Analytics by Category	✅	✅	✅
Analytics by Month	🔄 In progress	🔄 In progress	⏳ Pending
Logging & Monitoring	✅	—	—

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Development Approach

Features are built vertically — backend -> frontend -> tests — completing one feature end-to-end before starting the next. This ensures each slice of functionality is fully working and tested before moving on, and keeps the codebase in a continuously deployable state.

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