Optimizing a content index for target audience queries

Apparatus and methods are provided for indexing electronic content to be served to users' mobile and/or stationary communications and computing devices. An index is composed of multiple slices, with each slice storing multiple entries and each entry representing one content item or one campaign or collection of content items. An entry is populated with tokens representing attribute/value pairs of a target audience of the content item and/or property/value pairs of the item or the item's campaign. A query or request to identify content items for serving to a particular user is similarly formatted with tokens representing attribute/value pairs of the user and/or item/campaign. Queries can then be executed rapidly across any or all index entries in any or all slices. Within a slice, entries may be sorted by value or score, and integer components within an individual entry may be sorted to facilitate rapid comparison with a query.