A computer-implemented method of updating one or more index servers in order to reduce database load comprising: by one or more computing devices, receiving an update of user activity associated with one or more content objects associated with a search term, the user activity comprising one or more interactions by one or more users of an online social network with one or more content objects, wherein the content objects are of a plurality of different content-object types, and wherein each content object is indexed on a particular index server of a plurality of index servers; by one or more computing devices, responsive to receiving the update, indexing the one or more content objects on an update layer on a particular index server of a plurality of index servers, wherein each of the index servers stores a list of identifier information corresponding to content objects of a single content-object type of the plurality of different content-object types, and wherein the update layer indexes recent activity and comprises identifier information of the one or more content objects associated with the update; by one or more computing devices, determining whether the search term has a number of associated content objects indexed on the update layer of the particular index server exceeding a pre-determined threshold number, wherein the pre-determined threshold number is determined based on the content-object type of the content objects associated with the particular index server; and by one or more computing devices, at one or more pre-determined times, promoting the identifying information from the update layer to a base layer, wherein the base layer indexes activity previously indexed by the update layer and comprises identifying information of only a single content-object type, and wherein the base layer comprises identifier information of one or more other content objects of the single content-object type previously associated with the search term. by one or more computing devices, receiving an update of user activity associated with one or more content objects associated with a search term, the user activity comprising one or more interactions by one or more users of an online social network with one or more content objects, wherein the content objects are of a plurality of different content-object types, and wherein each content object is indexed on a particular index server of a plurality of index servers; by one or more computing devices, responsive to receiving the update, indexing the one or more content objects on an update layer on a particular index server of a plurality of index servers, wherein each of the index servers stores a list of identifier information corresponding to content objects of a single content-object type of the plurality of different content-object types, and wherein the update layer indexes recent activity and comprises identifier information of the one or more content objects associated with the update; by one or more computing devices, determining whether the search term has a number of associated content objects indexed on the update layer of the particular index server exceeding a pre-determined threshold number, wherein the pre-determined threshold number is determined based on the content-object type of the content objects associated with the particular index server; and by one or more computing devices, at one or more pre-determined times, promoting the identifying information from the update layer to a base layer, wherein the base layer indexes activity previously indexed by the update layer and comprises identifying information of only a single content-object type, and wherein the base layer comprises identifier information of one or more other content objects of the single content-object type previously associated with the search term.