Everything in inventory driven marketing rests on one technical fact: Shopify tells you, in real time, every time stock moves. The webhook system emits events for inventory level updates, product changes, and order activity, and any system subscribed to those events knows the state of the warehouse second by second. The marketing question is which events deserve a campaign and which are noise.
The Events That Matter
Four event patterns carry marketing weight. A stock level crossing zero upward is a restock, the trigger for back in stock notifications. A stock level crossing a configured floor downward is a low stock event, the trigger for urgency campaigns. A product creation event is a new arrival, the trigger for an announcement to the right category segment. And while not a single webhook, the daily aggregation of order events yields velocity, the input for overstock and trending detection. Everything else, the constant small fluctuations of normal selling, should be absorbed silently.
Thresholds Are the Difference Between Signal and Spam
A naive webhook integration fires on everything and trains the team to ignore it. The routing layer, built in n8n, applies thresholds before anything reaches Klaviyo: low stock means below N units and below N days of cover at current velocity, restock means at least N units returned (not a single returned order), price drop means at least a meaningful percentage. Variant level identity is preserved through the whole chain, so triggers and segments match at the level customers actually shop. Only events that clear the rules become Klaviyo custom events; the rest are logged and dropped.
The full event map, from webhook subscription to Klaviyo flow activation, is the architecture documented on our inventory driven marketing engine page.