Case study · Measurement & Data Infrastructure
Teaching the media plan to check the shelf before it spends.
A womenswear brand in fashion e-commerce, designing and selling plus-size clothing online from the United Kingdom.
The situation
The brand's dresses sell across many sizes and styles, and a successful ad can empty specific size variants in days. Stock lived in the commerce platform, campaigns lived in the ad platforms, and keeping the two aligned was manual work that could not keep up: ads kept promoting products customers could no longer buy, frustrating shoppers and wasting budget, while restocked or slower-moving styles waited their turn.
The assumption
Paid media doctrine says back your winners: when an ad performs, scale it. Nobody expected the media plan to consult the warehouse, because performance marketing optimises to the metrics it can see, and inventory has never been one of them.
What the evidence showed
Joining the commerce platform's sales and inventory data in BigQuery showed the two systems quietly working against each other. Bestsellers kept absorbing budget as their popular sizes sold out, so the spend increasingly advertised unavailable products. Meanwhile styles with healthy stock and genuine sales momentum sat under-promoted. The best-performing ad and the best use of the next pound were not the same thing, and the gap between them was invisible to both teams.
What we did
- i.Piped sales and inventory data from the Shopify store into BigQuery, joining two datasets that normally live in separate worlds.
- ii.Built views of top sellers over 7, 14 and 30 days against live stock on hand, down to individual size and colour variants, flagging products at risk of selling out.
- iii.Inverted the same analysis to surface styles with high stock and rising sales, ready to be promoted harder while bestsellers restocked.
- iv.Visualised the demand-versus-supply tension in a Looker Studio dashboard every stakeholder can read in real time, with flexible date ranges.
Results
Ad spend now follows sellable momentum instead of raw performance: campaigns pause before a size sells out rather than after, and under-promoted styles with stock behind them get their share of budget. The same dashboard tightened inventory decisions on the business side. Fewer disappointed customers, less budget spent marketing empty shelves.
The lesson
The best-performing ad is not always the best use of money. Spend should know what is on the shelf.