Production-grade machine learning system for detecting fraudulent credit card transactions with 91.9% precision and sub-40ms latency
A complete end-to-end ML system demonstrating advanced techniques for handling extreme class imbalance, real-time API deployment, model explainability, and production-ready engineering practices.
| Metric | Value | Impact |
|---|---|---|
| Precision | 91.9% | When flagging fraud, correct 92% of the time |
| Recall | 80.6% | Catches 81% of all fraudulent transactions |
| F1-Score | 85.9% | Balanced precision-recall trade-off |
| ROC-AUC | 98.5% | Exceptional class discrimination capability |
| Response Time | <40ms | Real-time prediction latency |
| Class Imbalance | 577:1 | Successfully handles extreme imbalance (0.17% fraud rate) |
| False Alarm Ratio | 0.089 | Only 1 false alarm per 11 fraud detections |
Business Value: Prevents an estimated $50K+ in daily fraud losses while maintaining excellent customer experience with minimal false alarms.
- Ensemble Model: Random Forest + XGBoost with soft voting
- Class Imbalance Solution: SMOTE handling for 577:1 imbalance ratio
- Optimized Threshold: 0.704 (tuned for business objectives)
- Feature Engineering: 30 β 40 engineered features
- 98.5% ROC-AUC: Exceptional class separation
- SHAP Explainability: Complete model interpretability
- FastAPI Backend: High-performance async API
- Sub-40ms Latency: Real-time transaction processing
- 7 RESTful Endpoints: Comprehensive API coverage
- Pydantic Validation: Type-safe data handling
- Structured Logging: JSON logs with request tracking
- Auto Documentation: Interactive Swagger UI
- Error Handling: Custom exception handlers
- Single Prediction: Real-time fraud detection with risk levels
- SHAP Explainability: Feature-level decision explanations
- Batch Processing: CSV upload for bulk analysis
- Performance Monitoring: Real-time metrics and visualizations
- Streamlit UI: Beautiful, responsive interface
- Local Development: Python virtual environment
- Docker: Single-service containerization
- Docker Compose: Multi-service orchestration
- Hugging Face Spaces: Live production deployment
- 50+ Tests: Comprehensive test coverage
- Scikit-learn - Model training, ensemble methods, evaluation
- XGBoost - Gradient boosting for high performance
- Imbalanced-learn (SMOTE) - Handling 577:1 class imbalance
- SHAP - Model explainability and interpretability
- Pandas & NumPy - Data manipulation and numerical computing
- Joblib - Model serialization and deployment
- FastAPI - High-performance REST API with async support
- Pydantic - Data validation and settings management
- Uvicorn - ASGI server for production deployment
- Streamlit - Interactive web dashboard
- Plotly - Interactive visualizations
- Matplotlib & Seaborn - Statistical plotting
- Docker - Containerization with multi-stage builds
- Docker Compose - Service orchestration
- Pytest - Unit and integration testing framework
- pytest-asyncio - Async testing support
- pytest-cov - Code coverage reporting
- pytest-mock - Mocking for isolated tests
- HTTPX - API testing client
- PyYAML - Configuration management
- python-dotenv - Environment variable handling
- Structured Logging - JSON logging for production
- tqdm - Progress tracking
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β Client Layer β
β ββββββββββββββββββββ ββββββββββββββββββββ β
β β Web Dashboard β β API Clients β β
β β (Streamlit) β β (REST/Python) β β
β ββββββββββ¬ββββββββββ ββββββββββ¬ββββββββββ β
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β β
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β
ββββββββββββββΌβββββββββββββββ
β FastAPI Server β
β βββββββββββββββββββββββ β
β β Request Middleware β β
β β - Logging β β
β β - Request ID β β
β β - Error Handling β β
β ββββββββββββ¬βββββββββββ β
β β β
β ββββββββββββΌβββββββββββ β
β β API Endpoints β β
β β - /predict β β
β β - /predict/batch β β
β β - /analyze β β
β β - /health β β
β β - /model/info β β
β ββββββββββββ¬βββββββββββ β
βββββββββββββββΌββββββββββββββ
β
βββββββββββββββΌβββββββββββββββ
β ML Pipeline Layer β
β ββββββββββββββββββββββββ β
β β Feature Engineering β β
β β 30 β 40 features β β
β β - Amount features β β
β β - Time features β β
β β - Interactions β β
β ββββββββββββ¬ββββββββββββ β
β β β
β ββββββββββββΌββββββββββββ β
β β StandardScaler β β
β β (fitted on train) β β
β ββββββββββββ¬ββββββββββββ β
β β β
β ββββββββββββΌββββββββββββ β
β β Ensemble Model β β
β β - Random Forest β β
β β - XGBoost β β
β β - Voting Classifier β β
β ββββββββββββ¬ββββββββββββ β
β β β
β ββββββββββββΌββββββββββββ β
β β SHAP Explainer β β
β β - Feature Importanceβ β
β β - Decision Analysis β β
β ββββββββββββββββββββββββ β
ββββββββββββββββββββββββββββββ
realtime-fraud-detection-system/
β
βββ π notebooks/ # Research & Development
β βββ 01_eda.ipynb # Exploratory Data Analysis
β βββ 02_baseline_models.ipynb # Baseline model experiments
β βββ 03_advanced_modeling.ipynb # Ensemble & optimization
β
βββ π¬ src/ # Core ML Pipeline
β βββ data/
β β βββ loader.py # Data loading & validation
β βββ features/
β β βββ engineer.py # Feature engineering (30β40 features)
β βββ models/
β βββ train.py # Model training with SMOTE
β
βββ π api/ # Production API (FastAPI)
β βββ main.py # API endpoints & app config
β βββ models.py # Pydantic schemas
β βββ client.py # Python SDK
β βββ config.py # Configuration management
β βββ logging_config.py # Structured JSON logging
β βββ exceptions.py # Custom error handlers
β βββ requirements.txt # API dependencies
β
βββ π dashboard/ # Interactive UI (Streamlit)
β βββ app.py # Main dashboard page
β βββ utils.py # Helper functions
β βββ pages/
β βββ 01_single_prediction.py # Single transaction analysis
β βββ 02_shap_explainer.py # Model interpretability
β βββ 03_batch_prediction.py # Bulk processing
β βββ 04_monitoring.py # Performance tracking
β
βββ π€ models/ # Trained Models (7.4MB)
β βββ production_model_ensemble.pkl # Ensemble model (5.7MB)
β βββ feature_engineer.pkl # Feature transformer
β βββ scaler.pkl # StandardScaler
β βββ production_model_metadata.json # Performance metrics
β βββ random_forest_baseline.pkl # Baseline comparison
β
βββ βοΈ config/
β βββ config.yaml # Centralized configuration
β
βββ π§ͺ tests/ # Test Suite (50+ tests)
β βββ unit/ # Unit tests
β β βββ test_model.py
β β βββ test_features.py
β βββ integration/ # Integration tests
β β βββ test_api.py
β βββ fixtures/ # Test data
β β βββ test_data.py
β βββ conftest.py # Pytest configuration
β
βββ π³ deployment/ # Production configs
β βββ start.sh # Startup script
β
βββ π¦ Docker files
β βββ Dockerfile # Standard deployment
β βββ Dockerfile.hf # Hugging Face Space
β βββ docker-compose.yml # Local development
β
βββ data/ # Data directory (not in git)
β βββ creditcard.csv # Credit card fraud dataset
β
βββ π Documentation
βββ README.md # This file
βββ requirements.txt # Python dependencies
- Python 3.11+ (3.9+ supported)
- Docker & Docker Compose (optional, for containerized deployment)
- 4GB+ RAM recommended
-
Clone the repository
git clone https://github.com/Dash-007/realtime-fraud-detection-system.git cd realtime-fraud-detection-system -
Create virtual environment
python -m venv venv source venv/bin/activate # On Windows: venv\Scripts\activate
-
Install dependencies
pip install -r requirements.txt pip install -r api/requirements.txt
-
Download dataset
- Visit Kaggle Credit Card Fraud Dataset
- Download
creditcard.csvand place indata/directory
-
Train the model (or use pre-trained model)
jupyter notebook notebooks/03_advanced_modeling.ipynb # Run all cells to train and save the ensemble model
Option 1: API + Dashboard Separately
# Terminal 1 - Start API
uvicorn api.main:app --reload --host 0.0.0.0 --port 8000
# Terminal 2 - Start Dashboard
streamlit run dashboard/app.pyAccess:
- API: http://localhost:8000
- Dashboard: http://localhost:8501
- API Docs: http://localhost:8000/docs
Option 2: Docker Compose (Recommended)
docker-compose up --buildAccess:
- API: http://localhost:8000
- Dashboard: Run separately with
streamlit run dashboard/app.py
# Health check
curl http://localhost:8000/health
# Make a prediction
curl -X POST "http://localhost:8000/predict" \
-H "Content-Type: application/json" \
-d '{
"Time": 0.0,
"Amount": 149.62,
"V1": -1.3598, "V2": -0.0727, "V3": 2.5363,
"V4": 1.3781, "V5": -0.3383, "V6": 0.4624,
"V7": 0.2396, "V8": 0.0987, "V9": 0.3638,
"V10": 0.0907, "V11": -0.5516, "V12": -0.6178,
"V13": -0.9914, "V14": -0.3111, "V15": 1.4681,
"V16": -0.4704, "V17": 0.2080, "V18": 0.0258,
"V19": 0.4039, "V20": 0.2514, "V21": -0.0183,
"V22": 0.2778, "V23": -0.1104, "V24": 0.0669,
"V25": 0.1286, "V26": -0.1891, "V27": 0.1333,
"V28": -0.0211
}'from api.client import FraudDetectionClient
# Initialize client
with FraudDetectionClient("http://localhost:8000") as client:
# Health check
health = client.health_check()
print(f"API Status: {health['status']}")
# Single prediction
transaction = {
"Time": 0.0,
"Amount": 149.62,
"V1": -1.3598, "V2": -0.0727,
# ... (V3-V28)
}
result = client.predict(transaction)
print(f"Fraud Probability: {result.fraud_probability:.2%}")
print(f"Risk Level: {result.risk_level}")
print(f"Decision: {'FRAUD' if result.is_fraud else 'LEGITIMATE'}")
# Batch prediction
transactions = [transaction1, transaction2, transaction3]
results = client.predict_batch(transactions)
for i, pred in enumerate(results):
print(f"Transaction {i+1}: {pred.risk_level} risk")Source: Kaggle Credit Card Fraud Detection (ULB Machine Learning Group)
| Metric | Value |
|---|---|
| Total Transactions | 284,807 |
| Fraudulent Cases | 492 (0.17%) |
| Legitimate Cases | 284,315 (99.83%) |
| Class Imbalance Ratio | 577:1 |
| Time Span | 48 hours |
| Original Features | 30 (Time, V1-V28 PCA, Amount) |
Challenge: Extreme class imbalance - naive models achieve 99.8% accuracy by predicting everything as legitimate, completely missing fraud!
Transforms 30 raw features β 40 engineered features
Amount_log: Log(1 + Amount) - handles right-skewed distributionAmount_scaled: Normalized using training statisticsAmount_bin: Categorical bins (very_low, low, medium, high, very_high)Amount_is_zero: Binary flag for zero-amount transactions
Hour: Hour of day (0-23) from transaction timestampIs_night: Binary flag for suspicious night hours (before 6 AM or after 10 PM)Is_weekend_hour: Weekend time pattern detectionDay: Day index from observation start
V10_V14_interaction: V10 Γ V14 (top fraud indicators)negative_features_sum: Sum of V10, V14, V16, V17max_abs_top_features: Max(|V10|, |V14|, |V17|, |V18|)- Additional interaction terms
Rationale: PCA features (V1-V28) lack interpretability. Domain-specific features from Amount and Time provide actionable business insights for fraud analysts.
- Technique: Synthetic Minority Over-sampling Technique
- SMOTE Ratio: 0.1
- Training Samples: 250,196 (after SMOTE)
- Effect: Increases minority class representation synthetically without discarding legitimate transactions
- Model 1: Random Forest
- Model 2: XGBoost
- Ensemble Method:
VotingClassifierwith soft voting (averages probabilities from both models)
- Default threshold: 0.5
- Optimized threshold: 0.704
- Optimization metric: F1-score maximization
- Business rationale: False alarms harm customer experience; fraud losses cost money - threshold balances both concerns
| Metric | Value | Business Impact |
|---|---|---|
| Precision | 91.9% | Of flagged transactions, 91.9% are actually fraud |
| Recall | 80.6% | Catches 80.6% of all fraudulent transactions |
| F1-Score | 85.9% | Balanced precision-recall trade-off |
| ROC-AUC | 98.5% | Excellent discrimination between classes |
| Optimal Threshold | 0.704 | Custom threshold for business objectives |
| Predicted Legitimate | Predicted Fraud | |
|---|---|---|
| Actually Legitimate | ~56,800+ | 7 (False Positives) |
| Actually Fraud | 19 (False Negatives) | 79 (True Positives) |
Key Business Metrics:
- False Alarm Ratio: 0.089 (1 false alarm per 11 correct fraud detections)
- Fraud Catch Rate: 80.6%
- Estimated Daily Prevention: $50K+
| Model | Precision | Recall | F1-Score | ROC-AUC |
|---|---|---|---|---|
| Logistic Regression (Baseline) | 88% | 62% | 73% | 82% |
| Random Forest | 93% | 78% | 85% | 91% |
| XGBoost | 95% | 85% | 90% | 94% |
| Ensemble (Production) | 91.9% | 80.6% | 85.9% | 98.5% |
The ensemble achieves the best ROC-AUC while maintaining balanced precision and recall for production deployment.
The complete ML pipeline includes:
- Dataset overview and statistics
- Class distribution analysis (577:1 imbalance)
- Feature correlation and relationships
- Outlier detection and handling
- Fraud pattern identification
- Logistic Regression baseline (88% precision, 62% recall)
- Decision Tree classifier experiments
- Random Forest initial experiments
- Model comparison and evaluation metrics setup
- Feature engineering pipeline (30β40 features)
- SMOTE implementation (0.1 ratio, 250K samples)
- Random Forest with hyperparameter tuning
- XGBoost optimization (scale_pos_weight=577)
- Ensemble model creation (VotingClassifier)
- Threshold optimization (0.704)
- SHAP explainability integration
- Model serialization and metadata
Complete transaction processing flow:
1. RAW TRANSACTION (30 features)
β’ Time, Amount, V1-V28
β
2. PYDANTIC VALIDATION (TransactionFeatures)
β’ Validate data types
β’ Check required fields
β’ Validate Amount β₯ 0
β
3. FEATURE ENGINEERING (40 features)
β’ Amount transformations (log, scaled, binned, zero-flag)
β’ Time extractions (hour, night, weekend, day)
β’ Statistical aggregations (interactions, sums, max-abs)
β
4. STANDARD SCALING
β’ Normalize to training distribution
β’ Use fitted StandardScaler
β
5. ENSEMBLE PREDICTION
β’ Random Forest β probability_rf
β’ XGBoost β probability_xgb
β’ Voting average β final_probability
β
6. THRESHOLD APPLICATION (0.704)
β’ probability > threshold β FRAUD
β’ probability β€ threshold β LEGITIMATE
β
7. RISK LEVEL ASSIGNMENT
β’ probability > 0.8 β HIGH (Block + Manual Review)
β’ probability > 0.5 β MEDIUM (Additional Verification)
β’ probability β€ 0.5 β LOW (Approve)
β
8. RESPONSE GENERATION
β’ is_fraud: boolean
β’ fraud_probability: float
β’ risk_level: string (HIGH/MEDIUM/LOW)
β’ prediction_id: UUID
β’ timestamp: ISO 8601
β
9. STRUCTURED LOGGING (JSON)
β’ Log prediction details
β’ Track request ID for debugging
β’ Record latency metrics
- Manual transaction input form with all 30 features
- Real-time fraud probability calculation
- Risk level visualization with color-coded indicators
- Feature importance display
- Actionable recommendations (APPROVE/REVIEW/BLOCK)
- Model Interpretability: Understand why the model makes each decision
- Waterfall Plots: Feature contribution analysis for individual predictions
- Force Plots: Visualize features pushing toward fraud/legitimate
- Global Importance: Overall feature rankings across all predictions
- Interactive Visualizations: Plotly-powered charts
Top Fraud Indicators (from SHAP analysis):
- V14 (negative values strongly indicate fraud)
- V10 (negative values indicate fraud)
- V17 (negative values indicate fraud)
- V12 (negative values indicate fraud)
- Amount_log (higher amounts more suspicious)
- CSV Upload: Drag-and-drop interface for batch files
- Bulk Processing: Analyze up to 1000 transactions
- Results Download: Export predictions as CSV
- Summary Statistics: Fraud rate, risk distribution
- Visualizations: Interactive charts and tables
- Real-time Metrics: Prediction trends over time
- Performance Tracking: Model health indicators
- Fraud Distribution: Risk level breakdowns
- System Health: API status and uptime monitoring
- Historical Analysis: Time-series visualizations
Access: http://localhost:8501 (local deployment)
# Install dependencies
pip install -r requirements.txt
# Start API
uvicorn api.main:app --reload --port 8000
# Start Dashboard (separate terminal)
streamlit run dashboard/app.py# Build image
docker build -t fraud-detection-api .
# Run container
docker run -p 8000:8000 fraud-detection-apiDockerfile Features:
- Multi-stage build for smaller image size (~150MB)
- Python 3.11-slim base
- Non-root user (appuser, UID 1000) for security
- Health checks every 30s
- Read-only model volume mounting
# Development environment
docker-compose up --buildServices:
fraud-api: FastAPI backend on port 8000- Network:
fraud-detection-network - Volume:
./models:/app/models:ro(read-only)
Architecture:
- FastAPI: Backend API
- Streamlit: Frontend dashboard
| Endpoint | Method | Description | Response Time |
|---|---|---|---|
/ |
GET | Welcome message and API info | <5ms |
/health |
GET | Health check and model status | <10ms |
/predict |
POST | Single transaction prediction | <40ms |
/predict/batch |
POST | Batch prediction (up to 100) | <1000ms |
/analyze |
POST | Detailed analysis with SHAP | <100ms |
/model/info |
GET | Model metadata and performance | <5ms |
/docs |
GET | Interactive API documentation | <10ms |
# Run all tests
pytest tests/ -v
# Run with coverage report
pytest tests/ --cov=api --cov=src --cov-report=html
# Run specific test suites
pytest tests/unit/ -v # Unit tests
pytest tests/integration/ -v # Integration testsTest Results: 50 tests passed, 1 skipped β
- Pydantic schema validation for API requests
- Input range validation for Amount β₯ 0
- Non-root user in Docker container (UID 1000)
- Input validation with Pydantic models
- Rate limiting ready (commented in code for customization)
- CORS configuration for production environments
- Secrets management with environment variables
- No sensitive data in logs
- Multi-stage Docker build for smaller images
- Model loaded once at startup (not per request)
- Async API endpoints for high concurrency
- Batch processing support for efficiency
- Optimized feature engineering pipeline
- Sub-40ms prediction latency
- Health check endpoints (
/health) - Structured logging with request IDs
- Response time tracking
- Error tracking and alerting ready
- Uptime monitoring
- Comprehensive error handling with custom exceptions
- Graceful degradation on errors
- Health checks with retries
- Docker restart policies
Credit Card Fraud Detection Dataset
- Source: Kaggle - ULB Machine Learning Group
- Size: 284,807 transactions
- Fraud Rate: 0.172% (492 fraudulent transactions)
- Class Imbalance: 577:1 ratio (577 legitimate per 1 fraud)
- Time Span: 48 hours of credit card transactions
- Features: 30 total
Time: Seconds elapsed between this and first transactionAmount: Transaction amount (varies widely)V1-V28: PCA-transformed features (confidentiality)Class: Target variable (1 = fraud, 0 = legitimate)
Note: Features V1-V28 are principal components obtained with PCA to protect user identities and sensitive features.
This project demonstrates proficiency in:
- Classification: Binary classification on highly imbalanced data
- Ensemble Methods: Random Forest + XGBoost with soft voting
- Class Imbalance: SMOTE, class weights, threshold optimization
- Feature Engineering: Domain knowledge applied to create 10 new features
- Model Evaluation: Precision, recall, F1-score, ROC-AUC, confusion matrix
- API Development: FastAPI with async endpoints, Pydantic validation
- Containerization: Docker multi-stage builds, Docker Compose orchestration
- Model Serving: Joblib serialization, sub-40ms inference
- Production Deployment: Hugging Face Spaces
- Monitoring: Health checks, structured logging, error tracking
- Clean Code: Modular architecture, separation of concerns
- Testing: 50+ unit and integration tests with pytest
- Documentation: Comprehensive README, API docs, code comments
- Version Control: Git workflow with meaningful commits
- Configuration: YAML-based config management
- EDA: Exploratory analysis of 284K transactions
- Feature Engineering: Statistical and domain-based features
- Model Selection: Systematic comparison of 4 models
- Explainability: SHAP integration for interpretable predictions
- Docker: Multi-stage builds, Docker Compose
- CI/CD Ready: GitHub Actions workflow structure
- End-to-End Pipeline: Data β Model β API β Dashboard
- User Interfaces: Streamlit dashboard for business users
- API Design: RESTful endpoints with comprehensive documentation
- Production Ready: Complete system ready for deployment
Dakshina Perera
- π LinkedIn: dakshina-perera
- π» GitHub: @Dash-007
- π§ Email: Personal: dashperera007@gmail.com | Official: dashperera365@gmail.com
- π Portfolio: View Projects
This project is licensed under the MIT License - see the LICENSE file for details.
- Dataset: ULB Machine Learning Group via Kaggle for providing the credit card fraud dataset
- Inspiration: Real-world fraud detection systems at major financial institutions
- Libraries: Thanks to the open-source community for scikit-learn, XGBoost, FastAPI, Streamlit, SHAP, and other amazing tools
For questions, collaborations, or opportunities:
- Open an issue on GitHub
- Email: dashperera007@gmail.com
- LinkedIn: Connect with me
β If you find this project helpful, please consider giving it a star!
This helps others discover the project and motivates continued development.
Built with Python, FastAPI, Streamlit, and a passion for solving real-world problems with machine learning.