Is asynchrony in Python/FastAPI the same as concurrency?

Asynchronous programming in Python (for example, using async/await in FastAPI) is a mechanism that allows input/output operations to be performed without blocking the main thread. This means that while waiting for a response from a database or external API, the application can switch to executing other tasks.

Concurrency is a broader concept that refers to the ability of a system to perform multiple tasks simultaneously. Asynchronous programming is one way to achieve concurrency, especially effective for I/O-bound tasks.

Thus, asynchronous programming in FastAPI provides concurrency at the level of a single thread, allowing multiple requests to be processed in parallel without creating many threads or processes.

Example of an asynchronous handler in FastAPI:

from fastapi import FastAPI
import asyncio

app = FastAPI()

@app.get("/async")
async def async_endpoint():
    await asyncio.sleep(1)  # simulate a long operation
    return {"message": "Asynchronous response"}

Here, the server is not blocked while waiting and can serve other requests.