Abstract: In some embodiments, a mediator device is operable to receive a request for permission to serve a first advertisement associated with a first advertiser to a display device. The mediator device can set a lock indicator to an active state in response to receiving the request and send an indication of approval to serve the first advertisement. The mediator device can receive, at a later time, a request for permission to serve a second advertisement to the display device. The mediator device can decline to send an indication of approval to serve the second advertisement when the lock indicator is in the active state.