Fingerprinting duplicate bid requests across the supply chain

Fingerprinting duplicate bid requests across the supply chain

When one impression reaches your DSP through several SSPs, you need to recognize the duplicates to avoid bidding against yourself. There is no shared impression ID across SSPs, so you fingerprint.

How the fingerprint is built:
— Combine fields that are stable across resellers: publisher domain or app bundle, placement/ad-unit ID, user identifier (or hashed IP plus user-agent where no ID exists), and a coarse timestamp bucket (e.g., 250ms).
— Two requests sharing this composite within the bucket are, with high probability, the same auction routed through different paths.

What the analysis reveals:
— Duplication rate per publisher: 3-6 paths for the same impression is common on large open-exchange inventory.
— Fee transparency: the same impression often arrives at different prices through different chains; the spread exposes undeclared reseller margins.
— Self-competition: cases where your own bids on two paths both cleared the respective SSP floors and one inflated the price you ultimately paid.

The action:
— Rank paths per publisher by all-in cost and authorization (sellers.json and the SupplyChain object, which declare who is allowed to resell).
— Suppress bids on lower-ranked duplicate paths, keeping only the cleanest.

Why it matters: without de-duplication you treat one impression as several auctions, multiplying compute and occasionally bidding up your own clearing price. The fingerprint turns invisible duplication into a controllable cost.