Python Backend

Production Python backend services with FastAPI, SQLModel, async PostgreSQL, and GCP Cloud Run deployment.

Core Architecture

The non-negotiable pattern is the layered flow. Each layer only calls the layer directly below it — never skip layers.

Router → Service → Repository → Database

Layer	Responsibility	Constraint
Router	HTTP in/out, request validation, response mapping	No business logic, no direct DB access
Service	Business logic, orchestration	No SQLModel queries, no AsyncSession, no HTTP concerns
Repository	Data access, query building, ORM operations	No business logic, no HTTP-aware errors

Supporting constructs (not layers):