PickleShare is a small shelve-like datastore with concurrency support.

Like shelve, a PickleShareDB object acts like a normal
dictionary. Unlike shelve, many processes can access the database
simultaneously. Changing a value in database is immediately visible to
other processes accessing the same database.

Concurrency is possible because the values are stored in separate
files. Hence the "database" is a directory where all files are
governed by PickleShare.