REST Architecture

REST (Representational State Transfer) is a set of architectural constraints for designing network APIs: resources identified by URLs, operations expressed with HTTP verbs, stateless requests, and standard status codes. FastAPI maps these concepts directly onto route decorators.

Resources and URLs

A resource is a noun (user, order, product) and lives at a URL. Collections are plural, single items include an identifier:

• GET /users - list users
• GET /users/42 - read one user
• POST /users - create a user
• PATCH /users/42 - partial update
• DELETE /users/42 - delete

HTTP Verbs in FastAPI

from fastapi import FastAPI, status

app = FastAPI()

@app.get("/users")
def list_users():
    return []

@app.post("/users", status_code=status.HTTP_201_CREATED)
def create_user(name: str):
    return {"name": name}

@app.get("/users/{user_id}")
def read_user(user_id: int):
    return {"user_id": user_id}

@app.patch("/users/{user_id}")
def update_user(user_id: int, name: str | None = None):
    return {"user_id": user_id, "name": name}

@app.delete("/users/{user_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_user(user_id: int):
    return None

Status Codes

Conventions That Matter

• Use nouns, not verbs, in URLs: /orders, not /getOrders.
• Use query parameters for filtering and pagination: /orders?status=open&page=2.
• Return consistent JSON shapes: same field names, same error format everywhere.
• Keep requests stateless: each request carries everything needed (e.g., an auth token).

Summary

REST design in FastAPI means mapping HTTP verbs to route decorators (get, post, put, patch, delete), organizing URLs around noun resources with identifiers, and using the standard status code vocabulary. Follow the conventions and FastAPI handles the mechanical side while you focus on the domain.