A small database with in-memory indexes based on Designing Data-Intensive Application.
The only two available operations are get and put.
$ source hash-indexes.sh
$ put key value
$ get key # returns value
It uses bash associative arrays to keep an index of the database and should be faster in read than a simple database. Since indexes are not persisted the database is clean each time it is launched.
This readme file is 193% bigger than the database source code :).