Guarantees

Every package declares the guarantee tiers it sells at. The tier decides what the seller stands behind: the schedule, the audience, or neither.

Tier	Meaning
ng_preemptible	Non-guaranteed, may be preempted. Priced by clearance tier: the same package at different priority levels (and prices), each with a target clearance rate the seller stands behind statistically, not contractually.
guaranteed	Non-preemptible. The schedule is firm.
audience_guaranteed	Delivery guaranteed in the package currency. The seller's make-good policy (ADU weight, credit, policy reference) is attached to the package and enforced in the workflow.

The wire values live at the guarantee tier enum. Clearance tiers (P1, P2, P3; see the clearance tier enum) are the priority levels inside ng_preemptible: each P-tier is a preemption protection level with its own rate on the card, so a buyer chooses how much protection to pay for on the same package.

Currency and guarantee are independent axes: spots or impressions, each guaranteed or not. A non-guaranteed buy in an impression currency is the audience_as_aired case: you pay the CPM on the impressions the schedule actually delivers, with no make-good. See the deal model for the four types the two axes produce.

Guarantees settle in the declared currency: an audience-guaranteed buy in hh reconciles on Household impressions delivered, and shortfalls trigger the attached make-good policy. On cleared trades, make-goods pass through back-to-back; see Settlement.