What does AWS personalize "exploration_item_age_cut_off" hyperpaeameter mean?

Question

Here is how AWS docs define it: Specify the maximum item age in days since the latest interaction across all items in the Interactions dataset. This defines the scope of item exploration based on item age. Amazon Personalize determines an item's age based on its creation timestamp or, if creation timestamp data is missing, interactions data.

It's not clear whether the age is calculated using CREATION_TIMESTAMP or the date of the last interaction with the item. If I set this hyperparameter to 30 for example, does an item disappear from exploration 30 days after its CREATION_TIMESTAMP or 30 days after its last interaction?

Answer 1

From the documentation:

Amazon Personalize uses creation timestamp data (in Unix epoch time format, in seconds) to calculate the age of an item and adjust recommendations accordingly.

If creation timestamp data is missing for one or more items, Amazon Personalize infers this information from interaction data, if any, and uses the timestamp of the item’s oldest interaction data as the item's creation timestamp. If an item has no interaction data, its creation timestamp is set as the timestamp of the latest interaction in the training set and Amazon Personalize considers it a new item.

Since creation timestamp is an optional column, Personalize has to fallback to looking at interactions as a proxy for determining an item's age when creation timestamp is not available.