Python FastAPI Scalable API .cursorrules prompt file

Author: Felipe Pimentel

What you can build

Automated Deployment & CI/CD PipelineCross-Platform Mobile App FrameworkPydantic Schema Visualizer

Benefits

Synopsis

Developers skilled in web technologies will benefit by building a scalable, high-performance web application with a FastAPI backend and React/Tailwind frontend, following best practices and optimal project structure.

Overview of .cursorrules prompt

The .cursorrules file provides guidelines and best practices for developing scalable APIs and applications using Python, FastAPI, TypeScript, React, Tailwind, and Shadcn UI. It establishes key principles for code writing, such as using concise, technical responses with clear examples and preferring functional programming patterns over classes. It outlines the project structure for both the frontend and backend, detailing the technologies, directory structure, and important configuration files. It specifies code style and structure, performance optimization techniques, project conventions, as well as testing and deployment practices. These frameworks are intended to ensure efficient, maintainable, and high-performance development of APIs and web applications.

.cursorrules Content

You are an expert in **Python, FastAPI, scalable API development, TypeScript, React, Tailwind,** and **Shadcn UI**.### Key Principles- Write concise, technical responses with accurate examples in both Python and TypeScript.- Use **functional and declarative programming patterns**; avoid classes unless absolutely necessary.- Prefer **iteration and modularization** over code duplication.- Use descriptive variable names with auxiliary verbs (e.g., `is_active`, `has_permission`, `isLoading`, `hasError`).- Follow proper **naming conventions**:  - For Python: use lowercase with underscores (e.g., `routers/user_routes.py`). - For TypeScript: use lowercase with dashes for directories (e.g., `components/auth-wizard`).### Project Structure- **Frontend**: - **Language**: TypeScript - **Framework**: React - **UI Library**: Tailwind CSS, Shadcn UI - **Build Tool**: Vite - **Directory Structure**:  - `frontend/src/`: Main source code  - `frontend/src/index.html`: Main HTML file  - Configuration Files:   - `vite.config.ts`   - `tsconfig.json`   - `tailwind.config.js`   - `postcss.config.js`  - **Docker Files**:   - `Dockerfile`   - `Dockerfile.dev`- **Backend**: - **Language**: Python - **Framework**: FastAPI - **Database**: PostgreSQL - **Directory Structure**:  - `backend/src/`: Main source code  - `backend/tests/`: Tests  - `document-processor/`: Document processing utilities  - Environment Configuration:   - `.env` / `.env.example`: Environment variables  - Database Configuration:   - `alembic.ini`   - `ddialog.db`: SQLite database for local development  - **Docker Files**:   - `Dockerfile`   - `Dockerfile.dev`### Code Style and Structure**Backend (Python/FastAPI)**:- Use `def` for pure functions and `async def` for asynchronous operations.- **Type Hints**: Use Python type hints for all function signatures. Prefer Pydantic models for input validation.- **File Structure**: Follow clear separation with directories for routes, utilities, static content, and models/schemas.- **RORO Pattern**: Use the "Receive an Object, Return an Object" pattern.- **Error Handling**: - Handle errors at the beginning of functions with early returns. - Use guard clauses and avoid deeply nested if statements. - Implement proper logging and custom error types.**Frontend (TypeScript/React)**:- **TypeScript Usage**: Use TypeScript for all code. Prefer interfaces over types. Avoid enums; use maps instead.- **Functional Components**: Write all components as functional components with proper TypeScript interfaces.- **UI and Styling**: Implement responsive design using Tailwind CSS with Shadcn UI, adopting a mobile-first approach.- **Performance**: - Minimize `use client`, `useEffect`, and `setState` hooks. Favor server-side rendering where possible. - Wrap client components in `Suspense` with fallback for improved performance.### Performance Optimization**Backend**:- **Asynchronous Operations**: Minimize blocking I/O operations using async functions.- **Caching**: Implement caching strategies for frequently accessed data using Redis or in-memory stores.- **Lazy Loading**: Use lazy loading techniques for large datasets and API responses.**Frontend**:- **React Components**: Favor server-side rendering and avoid heavy client-side rendering where possible.- **Dynamic Loading**: Implement dynamic loading for non-critical components and optimize image loading using WebP format with lazy loading.### Project Conventions**Backend**:1. Follow **RESTful API design principles**.2. Rely on **FastAPI’s dependency injection system** for managing state and shared resources.3. Use **SQLAlchemy 2.0** for ORM features, if applicable.4. Ensure **CORS** is properly configured for local development.5. No authentication or authorization is required for users to access the platform.**Frontend**:1. Optimize **Web Vitals** (LCP, CLS, FID).2. Limit `use client` hooks to small, specific components for Web API access.3. Use **Docker** for containerization and ensure easy deployment.### Testing and Deployment- Implement **unit tests** for both frontend and backend.- Use **Docker** and **docker compose** for orchestration in both development and production environments. Avoid using the obsolete `docker-compose` command.- Ensure proper input validation, sanitization, and error handling throughout the application.