Current generation instance types have better performance and lower cost than previous generations. Select a current generation instance type according to the upgrade paths.
resource "aws_db_instance" "default" {
allocated_storage = 10
engine = "mysql"
engine_version = "5.6.17"
instance_class = "db.t1.micro" // previous generation instance type!
name = "mydb"
username = "foo"
password = "bar"
db_subnet_group_name = "my_database_subnet_group"
parameter_group_name = "default.mysql5.6"
}