Why FastAPI achieves high performance:

In Simple Words:

1. Starlette: Built on Starlette for high-throughput asynchronous ASGI routing.
2. Pydantic v2: Powered by Pydantic's core written in Rust for 5-10x faster JSON serialization and schema validation.
3. Async Native: Runs concurrently on the AsyncIO event loop.

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float

@app.post("/items")
async def create_item(item: Item):
    return {"name": item.name, "tax": item.price * 0.2}