Let me break down the key differences between these two approaches for running background workflows in your FastAPI application: 1. Deployments via API - This is a more "infrastructure-focused" approach - Uses Prefect's REST API to trigger pre-configured deployments - Requires deployments to be created and configured beforehand - Provides full access to Prefect's deployment features (scheduling, parameters, etc.) - Better for production environments where you want clear separation between workflow definition and execution - Workflows are tracked in Prefect UI with their own deployment IDs 2. Task Workers with .delay() - This is more of a "developer-focused" approach - Uses background task processing similar to Celery or other task queues - More immediate and direct - no need to create deployments first - Better for rapid development and testing - Tasks are executed by workers listening on specific topics - Good for simpler background processing needs Here's a quick example of each approach:

python
# Using Deployments via API
from prefect.client import get_client

async def trigger_workflow_via_api():
    async with get_client() as client:
        flow_run = await client.create_flow_run_from_deployment(
            deployment_id="your-deployment-id",
            parameters={"param1": "value1"}
        )
    return flow_run.id

# Using Task Workers with .delay()
from prefect import task
from fastapi import FastAPI

app = FastAPI()

@task
async def my_background_task(data):
    # Your task logic here
    pass

@app.post("/process")
async def process_data(data: dict):
    # This will run in the background
    task_run = await my_background_task.delay(data)
    return {"task_id": task_run.id}

Which to Choose? Choose Deployments via API when: - You need full deployment features (scheduling, retries, etc.) - You want clear separation between workflow definition and execution - You're working in a production environment - You need robust monitoring and tracking in the Prefect UI Choose Task Workers with .delay() when: - You want a simpler, more direct approach - You're in development/testing phase - You need quick background processing without deployment overhead - Your tasks are relatively straightforward and don't need complex deployment configurations Both approaches are valid, but they serve different needs. The deployment approach is more "enterprise-ready" while the task worker approach is more developer-friendly during development. Remember that both approaches require running Prefect workers to execute the tasks - the main difference is in how you trigger and manage the execution.