Is prefect usable as an alternative to serverless functions (blocking, low overhead flow calls)? Initially I thought you'd be able to trigger lightweight flows via the REST API and get the response, but it looks like it's primarily a job queue (like luigi/celery) meaning you'd have to poll for a response with a job ID which is obviously not optimal. The UI is really pretty and looks useful so we may end up using it for cron-style jobs, but I'm wondering what people do for smaller units of work that maybe don't need full tracking