La compra de subasta es una compra sin garantía.

The statement "Auction buying is a non-guaranteed purchase" is true. In programmatic advertising, auction-based buying (like real-time bidding or RTB) means that advertisers bid for ad impressions in real-time. There's no guarantee that their bid will win the impression, nor is there a guarantee of a specific number of impressions or a fixed price. This contrasts with guaranteed deals (like programmatic guaranteed or direct buys), where inventory and pricing are pre-negotiated and reserved. Therefore, the non-guaranteed nature is a defining characteristic of auction buying.