Abstract: Systems and methods of the present disclosure are directed generally to serving content items via a hierarchical content node structure. More specifically, systems and methods of the present disclosure facilitate generating several content nodes using content data (e.g., bids, budget, content items, keywords, etc.), organizing the content nodes in a custom hierarchy that includes the content nodes, and selecting a content item of a content node to provide as a candidate for display on a user device.

Abstract: Methods, systems, and apparatus include computer programs encoded on a computer-readable storage medium for conducting an experiment for a campaign. A method includes: identifying a campaign including one or more content items and current selection criteria; receiving an indication of a proposed modification to be made to the campaign; storing the proposed modification as a draft campaign including the proposed modification in a first structure that includes the differences that are proposed to the campaign and a second structure that represents the campaign with the proposed modifications applied; determining a split to be applied as between using current campaign parameters or current selection criteria for a first portion of received traffic and using the proposed modification in the draft campaign for a second portion of the received traffic; and conducting an experiment based on using received traffic and in accordance with the split.