Async Programming in FastAPI

What is Async Programming?

Async programming means a program can start a task and, while waiting for that task to finish, work on another task instead of waiting doing nothing.

In FastAPI, async programming is mainly useful for I/O operations such as API calls, database operations, and reading or writing files.

Work Flow: 

Request 1 → Waiting for API
                ↓
Request 2 → Processing
                ↓
Request 3 → Processing
                ↓
Request 1 → API response

Why is Async Important in FastAPI?

FastAPI is designed to handle many requests efficiently. Async programming is especially useful when your application performs I/O operations.

Common I/O operations are:

• Calling another API
• Accessing a database
• Reading files
• Sending network requests
• Calling an AI service

Synchronous Programming

In normal synchronous programming, a task generally waits for the previous task to finish.

Work Flow: 

Request 1→Wait→Finish→Request2→Wait→Finish

Example Async code:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def home():
return {"message": "Hello"}

Here:async tells Python that this function is asynchronous.