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Introduction
Use this rule to help reduce wasted ad spend when an advertised ASIN is at risk of running out of inventory. Instead of using a fixed inventory quantity, the rule looks at how many days of inventory you have left based on recent sales velocity.
This helps account for the fact that “low inventory” means different things for different products. For example, 100 units may be plenty for a slow-moving ASIN, but not enough for a product selling 80 units per day.
How the rule works
This rule estimates an ASIN’s days on hand, also called inventory runway.
Days on hand = current inventory ÷ estimated daily units sold
If the ASIN’s estimated days on hand falls below the threshold you choose, Perpetua can pause ads for that ASIN in the selected goal.
For example:
Current inventory | Estimated daily sales | Days on hand | If your threshold is 3 days |
100 units | 50 units/day | 2 days | Pauses |
100 units | 10 units/day | 10 days | Does not pause |
5 units | 1 unit/day | 5 days | Does not pause |
The threshold is based on time, not units. A fast-selling ASIN can be paused even if it still has a meaningful number of units available, while a slow-selling ASIN may stay active with fewer units because it has a longer runway.
Setting your inventory threshold
When creating the rule, choose the minimum amount of inventory runway you want to maintain. You can set the threshold in:
Days, from 1 to 70 days
Weeks, up to 10 weeks
If the ASIN’s estimated inventory runway drops below your threshold, the rule becomes eligible to pause ads for that ASIN.
What gets paused
A few important scope details:
The rule applies only to the goals selected
The same ASIN in a goal not in the rule is not affected.
It does not pause unrelated ads or goals.
It only reverses pauses that were made by this specific rule.
For example: if ASIN B012345678 appears in two different goals and the rule is created only in Goal A, the rule can pause that ASIN in Goal A but will not pause it in Goal B.
Choose automatic or approval-based pausing
When setting up the rule, you can choose how actions are applied.
Auto-apply: Perpetua automatically pauses eligible ASINs when the rule runs.
Manually Approve: Perpetua creates a pending recommendation instead of applying the pause immediately. You can review the action from the rule’s pending approval queue and choose whether to accept it.
How Perpetua estimates sales velocity
To calculate inventory runway, Perpetua estimates how quickly the ASIN is selling based on recent sales data. The calculation uses a recent lookback window and gives more weight to newer sales activity. Today and yesterday are excluded from the velocity calculation because sales and inventory data may not be fully settled yet.
Perpetua also excludes configured tentpole or event days from the velocity calculation. This helps prevent short-term spikes, such as Prime Day or other major promotional events, from making normal sales velocity look artificially high.
When the rule will not pause an ASIN
An ASIN must have reliable inventory and sales data before the rule will pause it. If the data is missing, stale, or not strong enough to calculate a trustworthy sales velocity, the rule skips the ASIN.
The rule will not pause an ASIN when:
Reason | What this means |
Inventory data is missing or too old | Perpetua will not pause ads if it cannot trust the current inventory level. |
There is no sales and traffic data | The rule cannot calculate sales velocity. |
There were 0 units sold in the lookback period | There is no meaningful sell-through rate to use. |
Total units sold are too low | The ASIN has not sold enough recently for the velocity estimate to be reliable. |
Sales history is too sparse | The ASIN does not have enough recent daily data across the lookback window. |
Recent activity is missing | The ASIN does not appear to have enough recent activity to confirm it is still active. |
The ASIN has no live ads in the goal | There is nothing for the rule to pause. |
The ASIN is already paused | No additional action is needed. |
Re-enabling ads
When the rule pauses an ASIN, Perpetua records the inventory level needed to re-enable it. Once live inventory rises back to or above that required amount, the rule can re-enable the ASIN within the same goal.
The rule only re-enables ASINs that it paused itself. If an ASIN was paused manually, paused by another rule, or paused by another system, this rule will not override that action.
Tentpole and event-day behavior
If event-day protection is enabled, the rule avoids pausing ads during configured tentpole periods.
This is useful because sales velocity during major events can be unusually high and may not represent normal demand. Suppressing pauses during these windows helps avoid overreacting to temporary spikes.
Re-enabling can still occur during an event window if inventory has recovered.
Compatibility and scope
This rule applies to:
Sponsored Products goals
Seller and vendor accounts
FBA, FBM, or both, depending on your selected inventory fulfillment setting
Where to review rule activity
You can review actions from the Rules area in Perpetua.
Use:
Rules → History to see actions that were applied
Rules → Pending Approval to review actions that require manual approval
The history includes rule actions such as pending, auto-applied, and accepted actions, along with timestamps.
