What is the difference between asynchronous and synchronous routes in FastAPI, and how does it affect the operation of the service?

In FastAPI, routes can be defined as synchronous (def) or asynchronous (async def).

• Synchronous routes execute sequentially and block the thread until the request is processed. This is suitable for simple operations or when high concurrency is not required.

• Asynchronous routes allow non-blocking operations using async and await. This is especially useful for I/O operations (e.g., database queries, external API calls), as it enables handling other requests without waiting for the current one to finish.

Impact on the service:

• Asynchronous routes improve performance and scalability under high load.
• Synchronous routes are simpler to implement but can become bottlenecks under heavy traffic.

Example of an asynchronous route:

from fastapi import FastAPI
import asyncio

app = FastAPI()

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

@app.get("/sync")
def sync_route():
    import time
    time.sleep(1)  # blocking operation
    return {"message": "Synchronous response"}