I have published my website on Amazon EC2 (Singapore region) and I have used MySQL RDS instance for the data storage. Everything is working very fine except performance.
It is worth noting that, for whatever reason, MySQL query cache is OFF by default in RDS. We learned that the hard way ourselves this week.
This won't help performance of your initial query, but it may speed things up in general.
To re-enable query cache:
query_cache_size
and query_cache_type
(Disclaimer: I am not a DBA so there may be additional things I'm missing here)