1. A system, comprising: a data processing apparatus including one or more computers; a computer storage system storing instructions that when executed by the data processing apparatus cause the data processing apparatus to perform operations comprising: generating, by the data processing apparatus, a first API call to an advertising service, the first API call requesting first entities corresponding to a campaign management entity; receiving a set of first entities in response to the first API call; storing the set of first entities in a local cache of the data processing apparatus; processing an instruction for a given request for second data associated with a particular first entity of the set of first entities; determining, after and based on the processing, that the second data associated with the particular first entity is not stored in the local cache; after and based on the determining: generating an expanded request for multiple sets of second data associated with a plurality of additional first entities in the set of first entities, each set of second data being for a given additional first entity and being different from the set of second data for at least one other additional first entity; and generating a single second API call to the advertising service that includes the given request and the expanded request, the single second API call being generated prior to processing a second request for the second data associated with one of the additional first entities; receiving the second data associated with each of the additional first entities and the second data for the particular first entity; and storing the second data for the additional first entities in the local cache.