I have two ideas. Here's number 1:
-- syndication articles are always posting and always deleting. this causes lots of writes and lots of fragmentation, causing new posts from real users to fill into holes on many-day-old disk pages, killing cache hit rates. MySQL (unlike "real" databases) doesn't let you group data records together physically on disk based on certain indexes.
-- syndication content isn't necessary to have super reliable.
-- we could have a cluster just for syndication without any slaves, without tons of redundant hardware. the advantage will be the real database clusters won't get so fragmented. the deleted articles (over 2 weeks old) will just be replaced with the new articles.
This is so easy to do, it's worth trying.
But first I need to make moveucluster.pl allow users to be migrated between clusters. Currently the tool only supports moving from "cluster 0".