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name: fastapi-code-structure description: Enforce enterprise-grade project structure (Dispatch style), dependency injection patterns, and async concurrency rules for FastAPI. version: 2.0.0 allowed-tools: "Read,Write"

FastAPI Enterprise Standards

1. Directory Structure

Do not structure by file type (routers/, models/). Structure by Domain Component. Refer to the standard layout: Read({baseDir}/assets/project_layout.txt) [9].

2. Concurrency Rules

• Async Safety: Never put blocking I/O (synchronous DB calls, heavy calculation) inside async def routes. This blocks the event loop [10].
• Remediation: If blocking code is necessary, define the route as def (sync) so FastAPI runs it in a threadpool [11].

3. Dependency Injection

Use dependencies for data validation against the DB, not just Pydantic validation. Decouple dependencies to maximize caching within the request scope [12]. File: assets/project_layout.txt src/ auth/ # Domain Component router.py # Endpoints service.py # Business Logic models.py # SQLAlchemy Models schemas.py # Pydantic Models dependencies.py # Component-specific DI billing/ # Domain Component router.py service.py config.py # Split BaseSettings main.py # App Factory

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