Question 1,555 of 724
How to Choose the Right S3 Server-Side Encryption Type
A company stores sensitive data in an S3 bucket that must be encrypted at rest. The security team requires that the encryption keys be rotated every 90 days and that access to the keys be auditable. Which solution meets these requirements with the LEAST operational overhead?
Quick Answer
The answer is SSE-KMS with a customer managed key and automatic key rotation. This solution meets the requirement for rotating encryption keys every 90 days because AWS KMS supports automatic annual rotation for customer managed keys, and you can optionally configure a custom rotation period of 90 days via a Lambda function or by using a new key alias, though the exam accepts the default annual rotation as meeting the intent with least overhead. On the AWS Certified Developer Associate DVA-C02 exam, this question tests your understanding of S3 server-side encryption types and their operational trade-offs: SSE-S3 cannot be rotated on a schedule, SSE-C forces you to manage keys yourself, and client-side encryption adds unnecessary complexity. A common trap is assuming SSE-S3 provides key rotation, but it only rotates the data key, not the master key. Memory tip: KMS = Key Management Service, so if you need to manage and rotate keys, think KMS.
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
✓
Use SSE-KMS with a customer managed key and enable automatic key rotation.
SSE-KMS with a customer managed key and automatic key rotation meets the requirements with the least operational overhead. SSE-KMS provides auditable access to keys via AWS CloudTrail, and automatic key rotation satisfies the 90-day rotation requirement without manual intervention. Option A (SSE-S3) is incorrect because S3-managed keys cannot be rotated on a schedule. Option B (client-side encryption) adds significant operational overhead for key management and rotation. Option C (SSE-C) requires the company to manage and rotate its own encryption keys, increasing complexity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use SSE-S3 with default encryption enabled.
Why it's wrong here
SSE-S3 keys cannot be rotated on a schedule.
- ✗
Use client-side encryption with the AWS Encryption SDK.
Why it's wrong here
Client-side encryption requires managing keys in the application.
- ✗
Use SSE-C with keys stored in AWS Secrets Manager.
Why it's wrong here
SSE-C requires client-side key management and is more overhead.
- ✓
Use SSE-KMS with a customer managed key and enable automatic key rotation.
Why this is correct
KMS automatic rotation meets the 90-day requirement and provides auditing.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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Same concept, more angles
4 more ways this is tested on DVA-C02
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 developer needs to encrypt data in an S3 bucket. The company requires that the encryption key be managed by AWS but with the ability to audit key usage. Which S3 encryption option should the developer use?
easy- ✓ A.Server-Side Encryption with AWS KMS (SSE-KMS).
- B.Client-side encryption.
- C.Server-Side Encryption with S3-Managed Keys (SSE-S3).
- D.Server-Side Encryption with Customer-Provided Keys (SSE-C).
Why A: SSE-KMS uses AWS KMS to manage the encryption key and provides CloudTrail logs for auditing key usage, meeting the requirement for AWS-managed keys with auditability. SSE-S3 uses S3-managed keys but does not provide separate audit logs for key usage. SSE-C requires the customer to provide their own keys, not AWS-managed. Client-side encryption occurs before data is sent to S3 and does not use S3's server-side encryption. Therefore, SSE-KMS (option A) is the correct choice.
Variation 2. A company wants to encrypt data at rest in an S3 bucket using server-side encryption. Which option provides the MOST control over the encryption key?
easy- A.SSE-KMS (AWS KMS keys)
- ✓ B.SSE-C (customer-provided keys)
- C.Client-side encryption
- D.SSE-S3 (S3-managed keys)
Why B: SSE-C (customer-provided keys) gives you the most control because you manage the encryption key yourself—you provide the key in each request, and AWS discards it after use. This means you have full lifecycle control over the key material, including rotation, deletion, and access policies, without AWS ever storing the key. In contrast, SSE-KMS and SSE-S3 rely on AWS-managed or AWS-controlled key stores, reducing your direct control.
Variation 3. A company wants to encrypt data at rest in an S3 bucket. Which AWS service can provide encryption keys that are managed by AWS and rotated automatically?
easy- ✓ A.SSE-KMS (Server-Side Encryption with AWS KMS)
- B.SSE-S3 (Server-Side Encryption with S3 Managed Keys)
- C.SSE-C (Server-Side Encryption with Customer-Provided Keys)
- D.Client-side encryption using AWS KMS.
Why A: SSE-KMS (Server-Side Encryption with AWS KMS keys) allows you to use AWS KMS to encrypt your S3 objects. AWS KMS provides AWS managed keys (such as `aws/s3`) which are managed by AWS and rotated automatically every year. Additionally, AWS KMS provides a complete audit trail of key usage via AWS CloudTrail, allowing you to track when and by whom a key was used. SSE-S3 also manages and rotates keys automatically, but it does not provide an audit trail of key usage.
Variation 4. A company wants to use AWS KMS to encrypt data in an S3 bucket. They need to rotate the CMK annually. Which key type should they use to enable automatic rotation?
medium- ✓ A.AWS managed key (aws/s3)
- B.Customer managed key (CMK)
- C.Custom key store
- D.AWS owned key
Why A: AWS managed keys (aws/s3) support automatic annual rotation automatically without any configuration. When you use an AWS managed key for S3, AWS KMS rotates the key material once every year, which satisfies the requirement for annual rotation without manual intervention.
Last reviewed: Jun 20, 2026
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