1. A system, comprising: a processor; and a non-transitory computer readable storage medium including computer-executable instructions which when executed by the processor cause the processor to perform operations comprising: storing a policy specifying a maximum number of overlay messages that can be stored in a cache for a live video stream of events occurring in real time, the live video stream distributed to a plurality of recipients via a first channel; receiving an overlay message that corresponds to the live video stream of events; determining not to store the received overlay message in the cache based on the cache including, for the live video steam, the maximum number of overlay messages specified by the policy; generating, by the computer system, an overlay stream in real time that includes a plurality of overlay messages that correspond to the events of the live video stream of events, one or more of the plurality of overlay messages stored in the cache; and publishing the overlay stream to the plurality of recipients via a plurality of second channels.