US Patent 11221983 Multi-level indexing of backup files

A system indexes a first backup file, created for a data object when a first time period expired, in a first level of a data structure. The system indexes a second backup file, created for the data object when a second time period expired, in a second level of the data structure, the second time period being shorter than the first time period. The system receives a request to restore the data object to a specified time. The system enables restoration of the data object by identifying a first indexed backup file associated with the specified time in the first level of the data structure, by identifying a part of the second level of the data structure corresponding to the first indexed backup file, and by identifying a second indexed backup file associated with the specified time in the part of the second level of the data structure.