FastAPI App Builder

FastAPI App Builder generates modern async Python APIs using FastAPI's full feature set. It produces structured, typed code that leverages Python's type hints for automatic validation and documentation.

Project Structure

Follows the domain-based layout: `app/api/` for route handlers, `app/core/` for config and security, `app/models/` for SQLAlchemy ORM models, `app/schemas/` for Pydantic schemas, and `app/services/` for business logic.

Pydantic v2 Models

Generates separate Request, Response, and DB schemas with model_config for strict validation. Field validators and model_validators handle complex business rules. Computed fields derive values without storing them.

Async SQLAlchemy

Uses SQLAlchemy 2.0 async engine with asyncpg (PostgreSQL) or aiosqlite. Repository pattern wraps sessions. Alembic auto-generates migrations from model changes with `--autogenerate`.

Dependency Injection

FastAPI's Depends() system is used for database sessions, current user resolution, permission checking, and rate limiting. Dependencies are composable and testable with override_dependencies in tests.

Background Tasks

Integrates Celery with Redis broker for heavy background work, or uses FastAPI's built-in BackgroundTasks for lightweight post-response operations.