A recurring problem I have had for several Fedora releases now is that Yum over time becomes slower and slower as more packages are installed. This is of course to be expected due to the DB growing, but in my case Yum has now become so slow that it is almost unusable. Normally, it takes 2-3 minutes just to install a single package. most of the time, this latency will take place between yum first being invoked, and the part where I am asked to accept that the packages are downloaded and installed. It thus seems to be a DB issue.