Abstract: Systems and methods for performing an updating process to an in-memory index are provided. Upon receiving notice of document modifications covered by an inverted index associated with a search engine, in the form of an update file, a representation of the modification is published onto various index serving machines. Each index serving machine receiving the update file determines if the modifications are applicable to the index serving machine. If an index serving machine determines that it contains mapping information corresponding to the modified documents, the index serving machine utilizes the update file and associated mapping information to update an in-memory index. In embodiments, the in-memory index is used to provide results to user queries in tandem with the inverted index. In some embodiments, an extra in-memory index is maintained that is revised with constantly incoming metadata updates and the existing in-memory index is periodically swapped with the revised in-memory index.