STX runs as a standard second price auction. STX selects the highest winning bidder based on the highest net bid submitted. The auction process may result in adjustments of the submitted bid price at the exchange’s discretion, but a winning bid will never be charged more than the amount submitted.
The exchange runs on a viewable CPM basis, and bidders will only be charged if their winning ad is viewable by IAB standards - 50% of pixels in view for at least 1 second.
Responses must be received within 120ms per auction, or will otherwise be considered to have timed out. High rates of timeouts or other errors may result in receiving a lower frequency of bid requests.