[huhtenberg]

Looks like a cdb variation that moves index to a separate file and therefore allows changing the database (to a degree) without requiring a rebuild.

[0] http://en.wikipedia.org/wiki/Cdb_%28software%29

[js2]

Indeed, from the README: We used to rely a lot on CDB (which is a really great piece of software). It performed blazingly quick and produces compact files. We only stopped using it when our data started growing close to the 4 GB limit

[ptramo]

A 64-bit port of cdb isn't too hard: https://github.com/pcarrier/cdb64