Send price-drop alerts from a real item-level change
Notify eligible shoppers only when the product they considered has a material, current, and purchasable price drop.
Skip this if Stores without reliable catalog price, product-interest, identity, and channel-permission data
A price-drop alert should represent one verifiable event: an eligible shopper considered an item, that item became meaningfully cheaper, and it is still purchasable at the stated price.
Keep this separate from back-in-stock. Availability and price are different promises with different triggers and failure cases. A product can return at the same price, fall in price while unavailable, or change only for a market or variant.
The rest of this lesson is available once the Atlas is unlocked.