I'm trying to scale our web application (PHP, MySQL, memcache) in a multi-region scheme. Currently we are using a setup with two EC2 instances behind an ELB and an RDS instance, all of them in US-EAST (Virginia) region.
We would like to have a presence in the EU (Ireland) region as well. This means at least a new EC2 instance there (identical to the others, serving the same application).
I have copied the desired AMI, setup the new instance, setup a same ELB configuration (required for SSL termination) and configured latency-based routing in Route53. And it works as suggested.
But, clients from EU have speed problems. This is due to the fact that the EU EC2 instances connect to the US-based RDS instance. As far as I know Amazon has not yet enabled RDS multi-region replication.
Do you have any suggestions on how to properly speed up the whole setup while using the single RDS instance?
Also, any ideas in general on how to scale things up? Ideally we would like to continue using the RDS technology for various reasons. Nevertheless, I am open to suggestions (I guess the next idea would be to host our own MySQL servers).