One or more techniques and/or systems are provided for indexing content based upon index features (e.g., temporal features, user engagement features, and/or outlier features), and/or for providing content within a search result interface based upon such index features and/or rankings. For example, user reaction data associated with content (e.g., a microblog message, a social network post, etc.) may be evaluated to generate a user engagement feature that may be constrained to a time window feature (e.g., the number of shares of a message within the first 10 minutes from publication of the message) to create an index feature for indexing the content within a content index. Responsive to the index feature corresponding to a search query, the content may be provided with search results for the search query. For example, the content may correspond to trending or breaking news associated with the search query.