Supply Path Optimization (SPO)

Supply path optimization (SPO) is the buy-side practice of consolidating spend onto the shortest, cleanest paths from advertiser to impression. The classic problem: a single impression on a publisher might be available through 5+ SSPs, some of which are direct integrations and some of which are reseller relayed through 1-3 intermediaries each taking a fee. A naive DSP bids equally everywhere and overpays on the long paths.

SPO turns that into a deliberate routing decision. The buyer ranks paths by (a) fee transparency — does the SSP publish sellers.json and respect ads.txt?, (b) tech-fee burden — what's the all-in take rate?, (c) latency and fill rate, (d) measurement parity. Top paths get the budget; long paths get downweighted or dropped.

SPO is structurally enabled by header bidding / unified auction. Without parallel auctions, the SSP order is the publisher's call, not the buyer's, and SPO has nothing to optimize. With parallel auctions, every SSP gets the same opportunity at the same time, and the buy-side can pick.

In DOOH, SPO is in its infancy — many advertisers don't yet have visibility into how many hops separate them from a screen. Trillboards exposes its sellers.json publicly and supports direct DSP integration through /support/developers/dsp-api to make SPO straightforward.