Mysql replication definitely sounds like a way to go, but I didn't know about traffic and then how network speeds would affect it. I'm sure I'll just have to do some testing and see what the results are. E.g., replication running between Fremont and Newark.

And "master-master"? I hadn't heard of that configuration. I'll look into it.

Unless you're doing a lot of truly massive queries, the databases will for practical purposes always be in sync. I don't think the latency between Newark and Fremont would be a factor at all.

I've designed my app to favor multiple, small queries (in general) rather than enormous all-in-one queries. The all-in-ones may be the best in isolation, but with smaller ones, other threads have a chance to run, including the replication.

Master-master is a technique whereby two (or possibly more) database instances are simultaneously masters. When one makes a write, the other duplicates it. Very handy for high availability across datacenters, and really very easy to set up since MySQL 5.0.

The MySQL docs say to only run a cluster locally. It's not just writing that is duplicated, but also locks and such. You don't want a zillion row locks being sent across the wire synchronously for one write.

cluster != master-master replication

I've yet to find a good solution that is open source and free for #2, but for any geo setups we have I use Zeus GLB.

Bit expensive though, which will probably deter most people. Amazing product but yeah, there aren't many options that I am aware of comparable to the Linode pricing.