# Ask Fastapi Architect

> FastAPI scaffolding. Pydantic V2, async database, dependency injection.

- Skill: `navanithans/ask-fastapi-architect` (Agent Skill, multi-file: 5 files)
- Install (CLI): `npx skillmds@latest add navanithans/ask-fastapi-architect`
- Raw SKILL.md: https://api.skillmd.com/api/skills/navanithans/ask-fastapi-architect/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: NavanithanS (https://skillmd.com/u/navanithans)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/navanithans/ask-fastapi-architect

---


<critical_constraints>
❌ NO global DB sessions → use Depends(get_db)
❌ NO manually instantiating services in routes → use Depends
❌ NO routes without response_model → prevents data leaks
✅ MUST use Pydantic V2 (model_config, ConfigDict)
✅ MUST use AsyncSession with select()
✅ MUST use alembic for migrations
</critical_constraints>

<structure>
app/
├── api/v1/endpoints/, api.py, deps.py
├── core/ (config, security)
├── db/ (session, base_class)
├── models/ (SQLAlchemy)
├── schemas/ (Pydantic)
├── services/ (business logic)
└── main.py
</structure>

<pydantic_v2>
```python
from pydantic import BaseModel, ConfigDict, Field

class UserCreate(BaseModel):
    model_config = ConfigDict(from_attributes=True)
    username: str = Field(..., min_length=3)
    email: str
```
</pydantic_v2>

<dependency_injection>
```python
@router.post("/", response_model=ShowUser)
async def create_user(
    user_in: UserCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_active_user)
):
    return await UserService.create(db, user_in)
```
</dependency_injection>

<async_db>
```python
result = await db.execute(select(User).where(User.id == user_id))
user = result.scalars().first()
```
</async_db>