My read-intensive application needs to scale horizontally. It will be deployed by various clients using Amazon EC2. My initial thought is that a basic setup will utilize one RDS instance and one EC2 instance. The EC2 (c1.medium) instance will run a webserver and a local MySQL read replica of the RDS server. The application is configured to use the RDS server for writes and localhost for reads. Using an autoscaling group, more c1.medium EC2 instances are booted according to load. Every new EC2 instance will have its own local mysql replicated data for reading.
Now the question: can I hook into RDS to create local read replicas?
The obvious alternative is to boot extra official read replica nodes using the RDS API, but I don't like that because then I would need to scale in steps of 2 machines instead of 1, which is more costly. Also, I prefer to have mysql read queries local because of the latency.