API Development

Caspian is built on top of FastAPI. Whether you need a dedicated backend service or hybrid API routes within your fullstack app, you have native access to high-performance async endpoints.

1

Backend-Only Mode

Best for when you want a standalone API service without the templating engine. This enables standard FastAPI features like automatic Swagger UI documentation by default.

Terminal
➜ ~ npx create-caspian-app@latest
...
? What is your project named? › my-api
? Would you like to create a backend-only project? » Yes

Swagger UI

Automatic interactive docs available at /docs.

Lightweight

Disables the HTML rendering engine for maximum raw throughput.

2

Fullstack Hybrid Routes

In a fullstack application, you can mix UI pages and API endpoints. Simply return a JSONResponse from your page function to bypass the HTML renderer.

src/app/api/users/index.py 
from fastapi import Request
from fastapi.responses import JSONResponse

# This function runs when you visit /api/users
def page(request: Request):
    # Perform your logic (DB queries, etc.)
    users = [
        {"id": 1, "name": "Jefferson"},
        {"id": 2, "name": "Alice"}
    ]
    
    # Return JSONResponse to bypass Caspian's HTML renderer
    return JSONResponse(content={"data": users})
How it works: Caspian checks the return type of your page() function. If it sees a FastAPI Response object (like JSONResponse), it skips the Jinja2 template engine entirely, giving you raw API performance.