Event-driven: reacting to change
An event automation is attached to something happening: a record created, a field changed, a message received, a stage advanced. It runs within moments and it is the right tool whenever the thing you care about is an action someone took.
The limitation is structural. If nothing happens, no event fires, and the automation is silent. Silence is exactly the failure mode most service businesses lose money to.
Scheduled: detecting absence
A scheduled sweep runs at a fixed interval and asks a question about the current state of the world: which leads have sat unassigned longer than the threshold, which estimates are four days old with no reply, which invoices crossed thirty days. Nobody did anything; that is the point.
Two things make a sweep safe. It must record what it already acted on, so the same record is not escalated on every cycle. And its interval must be honest — a sweep every five minutes means alerts are accurate to about five minutes, not to the second.
Future-dated work is a third pattern
'Send this the morning of the appointment' is neither an event nor a recurring sweep. It is a piece of work created now and executed later. The right implementation is a queued run with a scheduled time, picked up by a processor when the time arrives.
Storing it as a queued record rather than a timer in memory is what makes it survive restarts, makes it visible before it runs, and makes it cancellable.