1. A method for efficient handling of contacts stored in a database apparatus, comprising: providing a distributed memory apparatus; and storing compressed representations of contact identifiers in the distributed memory apparatus as two-level indexed data structures, wherein a first level of each data structure includes a first unique set of decreasing integers, wherein a second level of the data structure includes a plurality of unique sets of decreasing integers, wherein each of the plurality of unique sets is linked to one of the integers in the first unique set, wherein each integer in the first unique set represents a first portion of the contact identifier and each integer in the plurality of unique sets represent a second portion of the contact identifier