This module provides a facility for efficiently sharing mutable data between processes on one host. Data is organised as a key/value store, resembling a Perl hash. The keys and values are restricted to octet (Latin-1) strings. Structured objects may be stored by serialising them using a mechanism such as Sereal.

The data is represented in files that are mapped into each process's memory space, which for interprocess communication amounts to the processes sharing memory. Processes are never blocked waiting for each other. The use of files means that there is some persistence, with the data continuing to exist when there are no processes with it mapped.

The data structure is optimised for the case where all the data fits into RAM. This happens either via buffering of a disk-based filesystem, or as the normal operation of a memory-backed filesystem, in either case as long as there isn't much swapping activity. If RAM isn't large enough, such that the data has to reside mainly on disk and parts of it have to be frequently reread from disk, speed will seriously suffer. The data structure exhibits poor locality of reference, and is not designed to play nicely with filesystem block sizes.