[kingmanaz]

If any here think fleitz is joking, please pick up a used copy of Manis, Schaffer, and Jorgensen's "Unix Relational Database Management". The authors create a relational database with little more than awk, cat, grep, od, sed, spell, tail and a bit of bourne-shell glue. After covering the basics of tables and relational theory, the authors create a small-business accounting system. The database became a commercial product (/rdb) and is still sold and used today (allegedly in hospitals).

[fleitz]

And for 'object databases'/ Key value stores implemented on flat files, clone a git repo and cd .git/objects.

http://git-scm.com/book/en/Git-Internals-Git-Objects