Eli, thanks.
The package details key "last modified" is indeed updated to the time of the latest push to the package's git repository, see https://git.archlinux.org/aurweb.git/tree/aurweb/git/update.py#n92
So this would be a valid method for guaranteeing cache invalidation.
ah, great. so, my amended request would be for a packages-time.gz file (or, something of that ilk). if possible, that would be great. cheers, Greg ps -- some sizes: 280K packages-sorted.gz packages.gz gunzip'd, sort'd, gzip'd 308K packages-date.gz the 8 "date" digits are exactly the same on each line 344K packages.gz a recent packages.gz 636K packages-8md5sum.gz the 8 "date" digits are *completely* random (from md5sum) 1.5M packages-md5sums.gz the 36 "md5sum" digits are completely random