As seth suggests set metadata_expire=reasonable number of seconds
in
your development repo definitions (to effect just those repos) or in
your main yum.conf(to effect all repos). The time based metadata
caching is a new feature for the 2.4.1 yum in rawhide. The default is
currently 8 hours, meaning yum won't attempt to refresh its metadata
for 8 hours after its last metadata refresh.
with this in mind, I think a new repo is needed on the main servers for
really hot security updates! That one could then have a 5 minute timeout
so that people aren't vulnerable for 8 hours.
Hot security fixes could then be in this "hot" repo for a day or two
until 1) the mirrors are synced and 2) the 8 hours are finished for all
mirrors, after which the package can be removed from the hot repo again,
so that in the normal case, the repodata is just a few (empty) bytes.