Because the file should be generated dynamically, maybe I should use the fs modules\'s writeStream. But I couldn\'t find any example codes with my poor googling. Sorry.
you don't need fs, just stream your data from db in request handler
you can set file metadata using Content-Disposition header
Content-Type: image/jpeg
Content-Disposition: attachment; filename=genome.jpeg;
modification-date="Wed, 12 Feb 1997 16:29:51 -0500";
Content-Description: a complete map of the human genome