Bolt DB Connection Failing AWS?

I've setup a local instance of bolt using config_local.yml and everything works great.

I've configured my AWS dev environment with config.yml but my EC2 instance can't connect to the DB using bolt (it works just fine if I mysql to the RDS database from the EC2 instance running bolt).

# app/config/config.yml
database:
  driver: mysql
  databasename: theDatabaseName
  username: theUserName
  password: thePassword
  hostname: myRDSInstance.myRDSHost.us-west-2.rds.amazonaws.com
  port: 3306

I'm 100% sure the credentials are correct (I tested it from the EC2 instance using mysql and it works perfectly.)

I've enable debugging in bolt but bolt-debug.log doesn't get created in app/cache (per the documentation in the config file).

Anyone have any thoughts?