1. A computer-implemented method in a content delivery (CD) network (CDN), said CDN comprising multiple CD services, said method operable on at least one device comprising hardware including memory and at least one processor, the method comprising: by a collector system: (A) receiving multiple event streams of event data, said multiple event streams comprising event data from a plurality of CD services in said CDN, said plurality of CD services including a first CD service, each event of said event streams comprising: (i) a timestamp for said event, (ii) information relating to said event; (B) producing state data relating to and based on information represented in said event data of said multiple event streams, wherein, while said collector system is producing said state data, said collector system asynchronously responds to at least one query relating to said state data; and (C) in response to a query from said first CD service, said query relating to said state data, providing at least some of said state data to said first CD service, wherein said state data are used to inform a peering policy of a set of peer caches.