Implement FastAPI Multi-Database API with MongoDB, MySQL, and PostgreSQL Support

.env.example

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+# Environment Configuration
+DATABASE_URL_MONGODB=mongodb://localhost:27017/fastapi_app
+DATABASE_URL_MYSQL=mysql://user:password@localhost:3306/fastapi_app
+DATABASE_URL_POSTGRESQL=postgresql://user:password@localhost:5432/fastapi_app
+
+# Application Settings
+APP_NAME=FastAPI Multi-Database API
+APP_VERSION=1.0.0
+DEBUG=True

Dockerfile

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+FROM python:3.11-slim
+
+# Set working directory
+WORKDIR /app
+
+# Install system dependencies
+RUN apt-get update && apt-get install -y \
+    gcc \
+    default-libmysqlclient-dev \
+    pkg-config \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy requirements and install Python dependencies
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+# Copy application code
+COPY . .
+
+# Expose port
+EXPOSE 8000
+
+# Run the application
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

README.md

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-# fastapi-mongo-mysql-postgresql-api
-FastAPI api application that uses 3 different databases as backend
+# FastAPI Multi-Database API
+
+A FastAPI application that demonstrates integration with three different database backends:
+- **MongoDB** (NoSQL document database)
+- **MySQL** (Relational database)
+- **PostgreSQL** (Relational database)
+
+## Features
+
+- 🚀 **FastAPI** - Modern, fast web framework for building APIs with Python 3.7+
+- 📊 **Three Database Support**: MongoDB, MySQL, and PostgreSQL
+- 🔄 **Async Operations** - Fully asynchronous database operations
+- 📝 **CRUD Operations** - Complete Create, Read, Update, Delete operations for each database
+- 🧪 **Testing** - Basic test suite included
+- 🐳 **Docker Support** - Docker Compose setup for easy development
+- 📚 **Auto-generated API Documentation** - Swagger UI and ReDoc
+
+## Project Structure
+
+```
+fastapi-mongo-mysql-postgresql-api/
+├── app/
+│   ├── database/           # Database connection modules
+│   │   ├── mongodb.py     # MongoDB connection
+│   │   ├── mysql.py       # MySQL connection
+│   │   └── postgresql.py  # PostgreSQL connection
+│   ├── models/            # Data models
+│   │   ├── mongo_models.py
+│   │   ├── mysql_models.py
+│   │   └── postgresql_models.py
+│   ├── routers/           # API route handlers
+│   │   ├── mongodb_routes.py
+│   │   ├── mysql_routes.py
+│   │   └── postgresql_routes.py
+│   └── config.py          # Application configuration
+├── tests/                 # Test suite
+├── main.py               # Application entry point
+├── requirements.txt      # Python dependencies
+├── docker-compose.yml    # Docker setup for databases
+├── Dockerfile           # Application container
+└── .env.example         # Environment variables template
+```
+
+## Quick Start
+
+### 1. Clone the Repository
+
+```bash
+git clone https://github.com/moreskylab/fastapi-mongo-mysql-postgresql-api.git
+cd fastapi-mongo-mysql-postgresql-api
+```
+
+### 2. Set up Environment
+
+```bash
+# Copy environment template
+cp .env.example .env
+
+# Edit .env file with your database configurations
+```
+
+### 3. Install Dependencies
+
+```bash
+pip install -r requirements.txt
+```
+
+### 4. Start Databases (using Docker)
+
+```bash
+# Start all databases
+docker-compose up -d
+
+# Check if containers are running
+docker-compose ps
+```
+
+### 5. Run the Application
+
+```bash
+# Development mode
+uvicorn main:app --reload
+
+# Production mode
+uvicorn main:app --host 0.0.0.0 --port 8000
+```
+
+### 6. Access the API
+
+- **API Documentation (Swagger)**: http://localhost:8000/docs
+- **Alternative Documentation (ReDoc)**: http://localhost:8000/redoc
+- **API Base URL**: http://localhost:8000
+
+## API Endpoints
+
+### Root Endpoints
+- `GET /` - API information and available endpoints
+- `GET /health` - Health check
+
+### MongoDB Endpoints
+- `POST /api/v1/mongodb/users/` - Create user
+- `GET /api/v1/mongodb/users/` - Get all users
+- `GET /api/v1/mongodb/users/{user_id}` - Get user by ID
+- `PUT /api/v1/mongodb/users/{user_id}` - Update user
+- `DELETE /api/v1/mongodb/users/{user_id}` - Delete user
+
+### MySQL Endpoints
+- `POST /api/v1/mysql/users/` - Create user
+- `GET /api/v1/mysql/users/` - Get all users
+- `GET /api/v1/mysql/users/{user_id}` - Get user by ID
+- `PUT /api/v1/mysql/users/{user_id}` - Update user
+- `DELETE /api/v1/mysql/users/{user_id}` - Delete user
+
+### PostgreSQL Endpoints
+- `POST /api/v1/postgresql/users/` - Create user
+- `GET /api/v1/postgresql/users/` - Get all users
+- `GET /api/v1/postgresql/users/{user_id}` - Get user by ID
+- `PUT /api/v1/postgresql/users/{user_id}` - Update user
+- `DELETE /api/v1/postgresql/users/{user_id}` - Delete user
+
+## Example Usage
+
+### Create a User in MongoDB
+
+```bash
+curl -X POST "http://localhost:8000/api/v1/mongodb/users/" \
+     -H "Content-Type: application/json" \
+     -d '{
+       "name": "John Doe",
+       "email": "john@example.com",
+       "age": 30
+     }'
+```
+
+### Get All Users from MySQL
+
+```bash
+curl -X GET "http://localhost:8000/api/v1/mysql/users/"
+```
+
+### Update a User in PostgreSQL
+
+```bash
+curl -X PUT "http://localhost:8000/api/v1/postgresql/users/1" \
+     -H "Content-Type: application/json" \
+     -d '{
+       "name": "Jane Doe",
+       "age": 25
+     }'
+```
+
+## Database Configuration
+
+### Environment Variables
+
+Create a `.env` file based on `.env.example`:
+
+```env
+# Database URLs
+DATABASE_URL_MONGODB=mongodb://localhost:27017/fastapi_app
+DATABASE_URL_MYSQL=mysql://user:password@localhost:3306/fastapi_app
+DATABASE_URL_POSTGRESQL=postgresql://user:password@localhost:5432/fastapi_app
+
+# Application Settings
+APP_NAME=FastAPI Multi-Database API
+APP_VERSION=1.0.0
+DEBUG=True
+```
+
+### Database Schemas
+
+#### User Model (Common structure across all databases)
+
+```json
+{
+  "name": "string",
+  "email": "string",
+  "age": "integer",
+  "created_at": "datetime" (auto-generated)
+}
+```
+
+## Testing
+
+```bash
+# Run tests
+pytest
+
+# Run tests with coverage
+pytest --cov=app
+```
+
+## Docker Deployment
+
+### Using Docker Compose (Recommended)
+
+```bash
+# Build and start all services
+docker-compose up --build
+
+# Start in background
+docker-compose up -d --build
+
+# Stop services
+docker-compose down
+```
+
+### Manual Docker Build
+
+```bash
+# Build the application image
+docker build -t fastapi-multi-db .
+
+# Run the container
+docker run -p 8000:8000 fastapi-multi-db
+```
+
+## Technologies Used
+
+- **FastAPI** - Web framework
+- **MongoDB** with **Motor** - Async MongoDB driver
+- **MySQL** with **aiomysql** + **SQLAlchemy** - Async MySQL driver
+- **PostgreSQL** with **asyncpg** + **SQLAlchemy** - Async PostgreSQL driver
+- **Pydantic** - Data validation and settings management
+- **Uvicorn** - ASGI server
+- **pytest** - Testing framework
+
+## Development
+
+### Adding New Endpoints
+
+1. Create new model in appropriate `models/` file
+2. Add database operations in corresponding `database/` module
+3. Create route handlers in appropriate `routers/` file
+4. Include router in `main.py`
+
+### Database Migration
+
+For SQL databases (MySQL/PostgreSQL), you can use Alembic for migrations:
+
+```bash
+# Initialize migrations
+alembic init alembic
+
+# Create migration
+alembic revision --autogenerate -m "Create users table"
+
+# Apply migrations
+alembic upgrade head
+```
+
+## Contributing
+
+1. Fork the repository
+2. Create a feature branch
+3. Make your changes
+4. Add tests
+5. Submit a pull request
+
+## License
+
+This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.

app/config.py

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+from pydantic_settings import BaseSettings
+from typing import Optional
+
+
+class Settings(BaseSettings):
+    app_name: str = "FastAPI Multi-Database API"
+    app_version: str = "1.0.0"
+    debug: bool = True
+
+    # Database URLs
+    database_url_mongodb: str = "mongodb://localhost:27017/fastapi_app"
+    database_url_mysql: str = "mysql://user:password@localhost:3306/fastapi_app"
+    database_url_postgresql: str = "postgresql://user:password@localhost:5432/fastapi_app"
+
+    class Config:
+        env_file = ".env"
+        case_sensitive = False
+
+
+settings = Settings()

app/database/mongodb.py

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+from motor.motor_asyncio import AsyncIOMotorClient
+from app.config import settings
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class MongoDB:
+    client: AsyncIOMotorClient = None
+    database = None
+
+
+mongodb = MongoDB()
+
+
+async def connect_to_mongo():
+    """Create database connection"""
+    try:
+        mongodb.client = AsyncIOMotorClient(settings.database_url_mongodb)
+        mongodb.database = mongodb.client.get_default_database()
+
+        # Test connection
+        await mongodb.client.admin.command('ping')
+        logger.info("Connected to MongoDB successfully")
+    except Exception as e:
+        logger.error(f"Error connecting to MongoDB: {e}")
+        # For demo purposes, we'll continue without failing
+        pass
+
+
+async def close_mongo_connection():
+    """Close database connection"""
+    if mongodb.client:
+        mongodb.client.close()
+        logger.info("Disconnected from MongoDB")
+
+
+async def get_database():
+    """Get database instance"""
+    return mongodb.database