Enable Encryption on an Unencrypted RDS Instance

A company stores sensitive data in an Amazon RDS for PostgreSQL DB instance. The security team requires that all data at rest be encrypted. The instance is currently unencrypted. What is the simplest way to enable encryption with minimal downtime?

Quick Answer

The correct answer is to create a snapshot of the DB instance, copy the snapshot with encryption enabled, and restore the snapshot to a new encrypted DB instance. This works because Amazon RDS does not support enabling encryption directly on an existing unencrypted instance; encryption must be applied at the snapshot level during a copy operation, which then propagates to the restored instance. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of RDS encryption limitations and the snapshot-based migration workflow—a common trap is assuming you can modify the instance directly or that you need complex tools like RDS Custom. Remember the key principle: encryption is a snapshot-level attribute, not an instance-level toggle. A useful memory tip is “snap, copy, restore—encrypt at the copy stage.”

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Create a snapshot of the DB instance, copy the snapshot with encryption enabled, and restore the snapshot to a new encrypted DB instance.

An existing unencrypted Amazon RDS instance cannot be directly encrypted. The standard approach to enable encryption with minimal downtime is to create a snapshot of the DB instance, copy the snapshot with encryption enabled, and restore the snapshot to a new encrypted DB instance. This process typically involves a brief outage during the restore but is simpler than other methods. Option B is incorrect because the AWS CLI does not support enabling encryption on an existing instance. Option C is incorrect because migrating to RDS Custom adds unnecessary complexity and does not directly enable encryption on the current instance. Option D is incorrect because the AWS Management Console also does not allow enabling encryption on an existing instance.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
Create a snapshot of the DB instance, copy the snapshot with encryption enabled, and restore the snapshot to a new encrypted DB instance.
Why this is correct
This is the standard procedure to enable encryption with minimal downtime.
✗
Use the AWS CLI to modify the DB instance and enable encryption.
Why it's wrong here
Modifying the instance does not support enabling encryption on unencrypted instances.
✗
Migrate the data to an Amazon RDS for PostgreSQL DB instance using RDS Custom.
Why it's wrong here
RDS Custom is not necessary and adds complexity.
✗
Modify the DB instance and enable encryption in the console.
Why it's wrong here
Modifying an existing Amazon RDS for PostgreSQL instance directly cannot enable encryption if it was originally provisioned unencrypted. Encryption is a fundamental configuration established at instance creation and cannot be altered post-provisioning for an unencrypted database. This option is tempting because the 'Modify DB instance' action is used for various parameter changes, but it only permits modifying an *already encrypted* instance's KMS key, or adjusting other non-encryption attributes like instance class or storage.

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Same concept, more angles

2 more ways this is tested on DBS-C01

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database contains sensitive data that must be encrypted at rest. Which action should the company take to enable encryption on the RDS instance?

easy

A.Modify the existing RDS DB instance and enable encryption.
✓ B.Create a new RDS DB instance with encryption enabled and migrate the data.
C.Enable Oracle Transparent Data Encryption (TDE) on the existing RDS instance.
D.Take a snapshot of the existing database, encrypt the snapshot, and restore from it.

Why B: Amazon RDS for Oracle supports encryption at rest using AWS KMS. Encryption can only be enabled when the DB instance is created; you cannot encrypt an existing unencrypted RDS instance. Therefore, to enable encryption for an existing on-premises Oracle database being migrated, you must create a new RDS DB instance with encryption enabled at launch and then migrate the data into that new instance. This makes option B the correct choice. Option A is incorrect because you cannot modify an existing unencrypted RDS instance to add encryption. Option C is incorrect because while Oracle Transparent Data Encryption (TDE) can be used to encrypt data within the database, it is not the native Amazon RDS encryption method and requires additional configuration; moreover, the scenario assumes a new RDS instance is being created, not an existing one. Option D is incorrect because the source database is on-premises, not an RDS instance, so there is no RDS snapshot to take; even if there were an existing unencrypted RDS instance, encrypting a snapshot requires copying it with encryption enabled, not directly encrypting the snapshot. Thus D is not a valid action for this migration.

Variation 2. A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database contains personally identifiable information (PII). The security team requires that the data be encrypted at rest using a customer-managed key stored in AWS KMS. Additionally, the team wants to ensure that the key can be rotated automatically every year. What should the company do to meet these requirements?

easy

A.Enable encryption on the RDS instance using the default RDS encryption and use AWS Secrets Manager to store the key.
✓ B.Create a customer-managed key in AWS KMS, enable automatic rotation, and enable encryption on the RDS instance using that key.
C.Create a customer-managed key in AWS KMS without automatic rotation, and manually rotate the key using the RDS console.
D.Use an AWS managed key for RDS and create an AWS Lambda function to rotate the key manually each year.

Why B: The correct approach is to create a customer-managed key in AWS KMS with automatic rotation enabled, then enable encryption on the RDS instance using that key. This meets the requirements for encryption at rest with a customer-managed key and automatic annual rotation. Option A is incorrect because AWS Secrets Manager is used for storing secrets, not encryption keys. Option C lacks automatic rotation. Option D uses an AWS managed key, not customer-managed, and requires a manual Lambda function, not automatic rotation.

Last reviewed: Jun 20, 2026

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