Systems and methods for regularly updating portions of a merged index are provided. Initially, upon receiving an indication that modifications have occurred to content of web-based documents, dynamic update of index (DUI) objects that identify the documents and expose the modified content are composed by ascertaining relative positions of the modified content within the documents, and packaging identifiers of the documents, the relative positions, and metadata underlying the modified content into a message. The DUI objects are applied to an overloading index that maintains structured records of recent modifications. In particular, portions of the overloading index are targeted utilizing the document identifiers and the relative positions specified by the DUI object, thereby updating the targeted portions within the overloading index corresponding to the modified content without rewriting the entire overloading index. Periodically, an association process is invoked for grouping the merged index with the overloading index for search purposes.