Fill Rate Is Not a Strategy

Fill rate answers one question. The business is usually asking another.

Fill rate tells you, of the opportunities sent to the auction, how many returned an ad. It does not tell you how much revenue the system generated across all of those eligible opportunities.

A floor is a minimum clearing price, not a quality filter. Lower the floor and more lower-priced demand can clear. Raise it too far and a $2 bid can become no-fill — observed eCPM rises, fill falls, and total revenue can fall with it. Neither outcome is automatically better. The question is whether the floor change improved revenue per eligible opportunity.

When we moved from waterfall to bidding, fill improved first. Revenue per eligible opportunity did not move at the same rate. That was the useful signal: more opportunities were clearing, but the additional fills were not creating proportional revenue.

Before chasing another point of fill, look at revenue per eligible opportunity. Then ask whether the next floor change improves that number — not whether the fill rate looks healthier.

Fill rate is a diagnostic of the auction. Revenue per eligible opportunity tells you whether the auction is creating more value.