QPS stands for queries per second. In digital advertising, it is a metric used to measure the rate at which a server processes incoming requests or queries within a specific period of time. In terms of RTB, QPS refers to the rate at which ad serving systems and ad exchanges process incoming bid requests from publishers, which has to be handled rapidly to facilitate real-time auctions. Maintaining a high QPS rate is essential for ensuring a positive user experience and maximizing revenue opportunities for publishers and advertisers. Ad tech platforms strive to maintain consistent QPS rates while minimizing errors, timeouts, and disruptions in ad-serving operations.