RDS will now go ahead and create a new read-replica for you.
Some parameters are inherited from the source instance and can't be defined at the time of creation:
- Storage engine
- Storage size
- Security group
The CLI command accepts some parameters that we could have defined, but didn't to keep things simple. They will instead be inherited from the source database. The main two are as follows:
- --db-instance-class: The same class as the source instance is used
- --db-subnet-group-name: The source instance's subnet group will be used and a subnet is chosen at random (hence, an Availability Zone is chosen at random)