What will happen when the modification is submitted?
The request will fail because this storage capacity is too large.
The request will succeed only if the primary instance is in active status.
The request will succeed only if CPU utilization is less than 10%.
The request will fail as the most recent modification was too soon.
Explanations:
The request will not fail because adding storage to an RDS instance is allowed even if the size is large, as long as it is within the AWS limits for storage.
The request can succeed regardless of the status of the primary instance. The modification happens in the background, and the database instance does not need to be in an active status for storage modification.
CPU utilization is irrelevant for modifying the storage capacity of an RDS instance. The modification only depends on the current storage and the requested size.
Modifications to the storage of an RDS instance are subject to a cool-down period. AWS has a limit on how quickly you can make storage changes, and making modifications too soon after a previous one will cause the request to fail.
It appears that the answer is:
The request will fail as the most recent modification was too soon.