Demand Sources in FAST: SSPs, DSPs, and Who Controls What

Created by Andrew Baritz, Modified on Wed, 7 Jan at 12:09 PM by Andrew Baritz

Demand Sources in FAST: SSPs, DSPs, and Who Controls What

At a glance
If you don’t know who controls the auction, you’ll waste time “optimizing” levers you don’t own. This article maps the actual control points for SSPs, DSPs, ad servers, and platforms in FAST.

Who this is for

FAST channel executives and operators making monetization partner decisions
Ad ops teams managing fill, floors, and deal strategy
Platform and partnership stakeholders aligning responsibilities

The minimum mental model

SSP (Supply-Side Platform): Represents your inventory to the market. Think “the seller’s marketplace.”
DSP (Demand-Side Platform): Where advertisers and agencies decide how to spend. Think “the buyer’s wallet + targeting brain.”
Ad server / SSAI decisioning: The logic that chooses which ad (or no ad) to play for a specific break.

Who controls what (practical version)

Lever	You can control	You cannot control
Floor prices	Yes (by SSP, deal type, geo/device, time-of-day)	Whether buyers are willing to pay it
Demand mix	Which SSPs, direct/PMP strategy, blocklists/allowlists	DSP budgets and pacing
Supply transparency	ads.txt/app-ads.txt, sellers.json alignment, schain hygiene	Buyer SPO preference and enforcement thresholds
Creative acceptance	Validation rules, spec enforcement, allowed durations	Quality of buyer creatives delivered

Walkthrough: How an ad gets from advertiser to your stream

Ad break starts (cue marker or schedule logic).
SSAI creates an opportunity (pod duration, device type, geo, content metadata).
SSP runs an auction (often OpenRTB under the hood).
DSP bids based on targeting, frequency, brand safety, and budget pacing.
Winning creative returns (often a VAST response, sometimes wrappers).
SSAI validates & stitches and playback proceeds.

Supply chain trust: why buyers punish messy setups

ads.txt / app-ads.txt tells buyers which sellers are authorized.
sellers.json lets buyers map seller IDs to real entities.
schain reveals the intermediary chain so buyers can enforce SPO.

Real-world demand setups (examples)

Example 1: Simple setup (good for early-stage channels)

1 primary SSP + 1 backup SSP
Floors modest, focus on fill stability
Strict creative spec enforcement to avoid device failures

Example 2: Mature setup (when you have scale)

Direct deals / PMPs for top geos and devices
Open auction as backfill
Separate floors by platform (Roku vs Samsung vs LG) because realized CPM can vary

Examples you can paste into tickets

Example: “SSP onboarding checklist”

Seller ID issued and confirmed
ads.txt/app-ads.txt line added (DIRECT/RESELLER correct)
sellers.json entry verified (SSP publishes correct entity)
schain expected path validated (where applicable)
Test pod: at least 10 filled ads across devices

Example: Floor grid (starter)

Segment	Open auction floor	PMP floor	Notes
US / CTV	$8	$18	Adjust after 7 days of fill data
CA / CTV	$5	$12	Often lower demand depth
ROW / CTV	$2	$6	Prioritize fill + watchability

Common pitfalls

Stacking SSPs without a plan: more hops can reduce bids.
Floors set too high: looks like “no demand” but is self-inflicted.
Reseller confusion: wrong DIRECT/RESELLER flags can block spend.