Every store has had the experience: a product suddenly takes off, a TikTok mention, a review, an influencer nobody briefed, and the team finds out when the monthly report lands, weeks after the spike. The momentum is gone, the algorithmic tailwind has passed, and the chance to pour fuel on a fire that lit itself was missed entirely. Trend detection is a timing problem, and monthly reporting is the wrong clock.
The Detection Math Is Simple
The mechanism is a daily comparison of each product's trailing 7 day sell rate against its trailing 30 day average. A ratio of 2x or higher is a trend candidate. The math is deliberately boring; the value is in running it every single day across every SKU and acting the same day, which no human team does manually. The daily job pulls sales velocity from the order data, computes the ratios, and flags the outliers before the morning standup.
The Inventory Check Before the Push
The step most trend playbooks miss: check the stock before amplifying. Pushing a trending product that has 30 units left manufactures a stockout and a wave of disappointed buyers. The automated flow checks inventory depth against the spiked velocity first. Enough stock: a trending campaign fires to a lookalike segment of similar buyers, with social proof copy generated from the real numbers, and the team gets a Slack nudge to consider an ad push. Not enough: the campaign holds and a reorder alert goes out instead, restock first, amplify second.
This is the third engine on our inventory driven marketing engine page, running alongside overstock clearance and low stock urgency on the same Shopify data layer.