If you need to remove a customer key from Astra DB Serverless, contact DataStax Support.

Contact DataStax Support to delete or rotate a customer key in your Astra DB organization. With your agreement, the DataStax Support team can delete the key on your behalf. When a registered association with your customer-managed key is deleted from your Astra DB organization, the default Astra DB data encryption provided by Astra DB is used.