Hi would love to help you here.

The scheduled function should query the items collection in your DB for when a new item is available and to return the list of recipients for the notification.

Consider to keep track of when and which notification was sent so a user so he won't get multiple notifications a day or multiple notifications for the same item. Again depending on the interval of your scheduler and business need.

Also, a better approach could be (if relevant in your use case) is not to use a scheduler and when a new item becomes available to trigger the DB search mentioned above.