What should the database specialist do to resolve this?
Disable automated backups in the DB instance. Share both the automated snapshot and the default KMS key with the staging account. Restore the snapshot in the staging account and enable automated backups.
Copy the automated snapshot specifying a custom KMS encryption key. Share both the copied snapshot and the custom KMS encryption key with the staging account. Restore the snapshot to the staging account within the same Region.
Modify the DB instance to use a custom KMS encryption key. Share both the automated snapshot and the custom KMS encryption key with the staging account. Restore the snapshot in the staging account.
Copy the automated snapshot while keeping the default KMS key. Share both the snapshot and the default KMS key with the staging account. Restore the snapshot in the staging account.
Explanations:
Disabling automated backups and sharing the default KMS key is not necessary. The issue can be resolved by copying the snapshot with a custom KMS key or modifying encryption settings.
Copying the snapshot with a custom KMS encryption key allows sharing with another account. The copied snapshot can be restored in the staging account with the custom KMS key.
Modifying the DB instance to use a custom KMS encryption key is not required for sharing the snapshot. Copying with a custom KMS key is sufficient.
The default KMS key cannot be shared across accounts. A custom KMS key is needed to share the snapshot with the staging account.
I infer that the answer is:
Copy the automated snapshot specifying a custom KMS encryption key. Share both the copied snapshot and the custom KMS encryption key with the staging account. Restore the snapshot to the staging account within the same Region.