There is only one file type that uses the .LRDB extension:
Adobe Lightroom Database
Data file created by Adobe Lightroom version 1, the first installment of the photo management application; stores information about a collection of images that have been imported into the software; enables storage of organized photo data.
Later versions of Lightroom use .LRCAT files for photo catalog information.
NOTE: Lightroom was formerly known as Photoshop Lightroom.
Updated: September 10, 2017