We've asked a similar question in the past, basically we have a very large Magento store with 500000 products which are currently reindexed once a day, during the night.

We'd like to speed this process up significantly, we're at about 4-5 hours now. The solution was suggested for us to do something like this on a server cluster and replicate the database changes after they've been done on a machine that isn't being bothered with serving customers.

But what is the mechanism for that? How do we replicate those changes across to the live site from the server cluster?

Can someone point me in the right direction here?