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.
First i highly recommend to look over these queries using
SHOW FULL PROCESSLIST
You can read more about it on SHOW FULL PROCESSLIST
This will show you the time each query take.
Then you can use
EXPLAIN
You can read more about it on EXPLAIN
This will show you if you need some enhancement on your queries