A new workflow only enrols people who trigger it from now on — unless you ask it to also take everybody who already matches. That option is offered when you save, and it is the single easiest way to email thousands of people by accident.
When backfilling is right
| Backfill | Do not backfill |
|---|---|
| A win-back sequence for lapsed customers — the whole point is the people already lapsed. | A welcome sequence. Everyone who bought in the last five years does not need welcoming. |
| A small, well-understood bucket. | Anything triggered by an event, where the moment has passed. |
| You have checked the count and are happy to email all of them today. | You are not sure how many people it would be. |
Before you say yes
LOOK AT THE NUMBER FIRST
A safer way
- Go live without backfilling.
- Watch the workflow for a week on new people only.
- Once you trust it, backfill deliberately — ideally against a narrower bucket first.
Timing matters too. A backfill that runs on a Friday evening lands in inboxes over the weekend and nobody is watching the replies on Saturday.