Inventory Reservations

Inventory reservations are stored on a per-FulfillmentGroupItem level and each FulfillmentGroupItem can have multiple reservations representing different quantities fulfilled at different locations. Inventory Reservations are persisted at checkout in order to store which location inventory was decremented from. This allows you to see exactly where your order should be fulfilled from on the backend.

Reservation Strategies

In order to customize how inventory reservations are distributed within a FulfillmentGroup, there is a common interface called the InventoryReservationStrategy. The out of the box strategies are:

Name	System Property Value
Single location per group	SINGLE_PER_GROUP
Single location per item	SINGLE_PER_ITEM
Multiple locations per item	MULTIPLE_PER_ITEM

To select between them, override the advanced-inventory.item.reservation.strategy system property with one of the above values:

advanced-inventory.item.reservation.strategy=SINGLE_PER_GROUP

The default strategy is SINGLE_PER_GROUP

Each of these strategies is documented in more detail below.

Customizing Reservation Strategies

A few steps to create your brand new reservation strategy:

Create a Spring bean that implements this InventoryReservationStrategy interface

Create a subclass of InventoryReservationStrategyType to add your own custom type

For instance:

public class MyReservationStrategyType extends InventoryReservationStrategyType {
    public static InventoryReservationStrategyType LOCATION_BASED = new InventoryReservationStrategyType("LOCATION_BASED", "Location Based");
}

Change the advanced-inventory.item.reservation.strategy system property to the value of your new InventoryReservationStrategyType

Following the above example that would be:
```
advanced-inventory.item.reservation.strategy=LOCATION_BASED
```

This component will then be automatically injected and used by the AdvancedInventoryServiceExtensionHandler.

Out of the Box Strategies

Consider the following data scenario:

Location 1

SKU_ID	Quantity
1	3
2	3

Location 2

SKU_ID	Quantity
1	1
2	1

Location 3

SKU_ID	Quantity
2	10

Single Location Per Group

This strategy is designed to ensure that for an entire Fulfillment Group must be fulfilled from the same location. In the example data above, this translates to the following:

Sku ID 1 can have a maximum quantity of 3 items within a fulfillment group
Sku ID 2 can sell a maximum of 10 items within a fulfillment group

So, the following order will succeed:

O_ID	FG_ID	FGI_ID	SKU_ID	Quantity
1	1	1	1	2
1	1	2	2	1

And would create the following inventory reservations:

FGI_ID	FL_ID	Quantity
1	1	3
2	1	1

But the this order would not suceed:

O_ID	FG_ID	FGI_ID	SKU_ID	Quantity
1	1	1	1	2
1	1	2	2	5

Even though Location3 has enough inventory to handle buying 5 of Sku2, it does not have any inventory for Sku1. This would put different items in a single fulfillment group in different locations and thus fail.

Single Location per Item

This strategy is slightly more flexible than the original, and allows for different items within a Fulfillment Group to be fulfilled from different locations. However, each location must have enough inventory to handle the quantity for that Sku. So the previously failed order would now succeed:

O_ID	FG_ID	FGI_ID	SKU_ID	Quantity
1	1	1	1	2
1	1	2	2	5

And create the following inventory reservations (notice the different locations for the fulfillment group items):

FGI_ID	FL_ID	Quantity
1	1	2
2	3	5

But this strategy would still fail given this order:

O_ID	FG_ID	FGI_ID	SKU_ID	Quantity
1	1	1	1	4

While the combination of Location1 and Location2 have a total quantity of 4 for Sku1, there is not enough for the entire quantity of the item to be fulfilled at a single location. We would have to split the fulfillment across multiple locations for a single item.

Multiple Locations per Item

This is the most flexible strategy and allows for a single item with multiple quantities to be fulfilled across different locations. The above scenario would now succeed:

O_ID	FG_ID	FGI_ID	SKU_ID	Quantity
1	1	1	1	4

And create the following inventory reservations:

FGI_ID	FL_ID	Quantity
1	1	3
1	2	1

Other Considerations

All of the out of the box InventoryReservationStrategy implementations prioritize inventory by either minimum or maximum quantity at a Fulfillment Location. You can easily customize this prioritization specifically with the advanced-inventory.prioritize.higher.quantity and advanced-inventory.prioritize.lower.quantity. If both of these system properties are false, inventory will not be prioritized
If you are using either the single location per group or single location per item, in order to retrieve the quantity available for a Sku the system uses the maximum quantity avilable at a single Fulfillment Location rather than sum up all the quantities for the Sku across all Fulfillment Locations. If you need to further customize this, subclass the AdvancedInventoryServiceExtensionHandler and override the blAdvancedInventoryServiceExtensionHandler bean.
The out of the box strategies can be somewhat non-deterministic if inventory counts are the same within each Fulfillment Location for an individual Sku