fastapi-patterns

What this skill does

When applied, it prepends a system prompt before your request is sent — no extra calls and no change to how you are billed beyond the added tokens.

---
name: fastapi-patterns
description: FastAPI patterns for async APIs, dependency injection, Pydantic request and response models, OpenAPI docs, tests, security, and production readiness.
origin: community
---

# FastAPI Patterns

Production-oriented patterns for FastAPI services.

## When to Use

- Building or reviewing a FastAPI app.
- Splitting routers, schemas, dependencies, and database access.
- Writing async endpoints that call a database or external service.
- Adding authentication, authorization, OpenAPI docs, tests, or deployment settings.
- Checking a FastAPI PR for copy-pasteable examples and production risks.

## How It Works

Treat the FastAPI app as a thin HTTP layer over explicit dependencies and service code:

- `main.py` owns app construction, middleware, exception handlers, and router registration.
- `schemas/` owns Pydantic request and response models.
- `dependencies.py` owns database, auth, pagination, and request-scoped dependencies.
- `services/` or `crud/` owns business and persistence operations.
- `tests/` overrides dependencies instead of opening production resources.

Prefer small routers and explicit `response_model` declarations. Keep raw ORM objects, secrets, and framework globals out of response schemas.

## Project Layout

```text
app/
|-- main.py
|-- config.py
|-- dependencies.py
|-- exceptions.py
|-- api/
|   `-- routes/
|       |-- users.py
|       `-- health.py
|-- core/
|   |-- security.py
|   `-- middleware.py
|-- db/
|   |-- session.py
|   `-- crud.py
|-- models/
|-- schemas/
`-- tests/
```

## Application Factory

Use a factory so tests and workers can build the app with controlled settings.

```python
from contextlib import asynccontextmanager

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

from app.api.routes import health, users
from app.config import settings
from app.db.session import close_db, init_db
from app.exceptions import register_exception_handlers


@asynccontextmanager
async 

Use this skill

{
  "model": "gpt-4o-mini",
  "skill": "imp-e6c04b08-9ca1-40c1-a315-465363d25761",
  "messages": [{ "role": "user", "content": "…" }]
}

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