What Is Fan-Out in Message Delivery?
Fan-out is delivering a single input to several destinations at once. One form submission becomes an email, a Slack message and a webhook call, each dispatched and retried on its own.
Independence is the point. If deliveries run in sequence and the second one fails, everything after it stalls behind a problem that has nothing to do with it. Run them in parallel and a Slack outage delays Slack, not the email that was supposed to go to your inbox.
Each destination then needs its own retry state, because they fail differently. A webhook to a server that is down deserves patient backoff. An email rejected for a bad address will never succeed and should stop immediately.
The receipt should not wait for any of it. Accept the submission, confirm it, then deliver in the background. A visitor should not be watching a spinner while a third-party API decides how it feels.
In WebForms
WebForms accepts and stores the submission first, then fans out through a queue with per-destination retries and backoff, so a failing destination never costs the submitter a slow page.