Quick Answer
The answer is the AWSServiceRoleForRDS service-linked role. This role is missing because RDS requires it to call AWS KMS on your behalf when launching an encrypted DB instance; without it, RDS lacks the IAM permissions to decrypt the KMS key, causing a KMS access failure. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how service-linked roles grant AWS services cross-service permissions—specifically, that RDS cannot assume a standard role to access KMS encryption keys. A common trap is assuming a customer-managed KMS policy or an IAM user role is the fix, but the root cause is the missing service-linked role, which is automatically created on first RDS resource creation but can be deleted. Memory tip: think “RDS needs its own role to reach KMS”—if the role is gone, encryption fails.
This SCS-C02 practice question tests your understanding of data protection. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security engineer is troubleshooting an issue where an Amazon RDS for MySQL DB instance encrypted at rest with AWS KMS is failing to launch. The error message indicates a KMS access issue. Which IAM role or policy is most likely missing?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The RDS subnet group is in a private subnet without a NAT gateway
Why wrong: Unrelated to KMS access.
The DB instance's security group does not allow outbound traffic to KMS
Why wrong: KMS is API-based, not network.
The KMS key policy does not grant access to the root account
Why wrong: Root always has access; key policy likely needs RDS service.
The AWSServiceRoleForRDS service-linked role is missing
Required for RDS to access KMS keys.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The AWSServiceRoleForRDS service-linked role is missing
The AWSServiceRoleForRDS service-linked role is required for RDS to call AWS KMS on your behalf to manage encryption keys for encrypted DB instances. If this role is missing, RDS cannot obtain the necessary permissions to decrypt the KMS key during instance launch, resulting in a KMS access error. This role is automatically created the first time you create an RDS resource, but if it was deleted or not present, you must recreate it to resolve the issue.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The RDS subnet group is in a private subnet without a NAT gateway
Why it's wrong here
Unrelated to KMS access.
The DB instance's security group does not allow outbound traffic to KMS
Why it's wrong here
KMS is API-based, not network.
The KMS key policy does not grant access to the root account
Why it's wrong here
Root always has access; key policy likely needs RDS service.
The AWSServiceRoleForRDS service-linked role is missing
Why this is correct
Required for RDS to access KMS keys.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often focus on KMS key policies or network configurations, but the real issue is the missing service-linked role that grants RDS the service-level permissions to interact with KMS, which is a common oversight in encrypted RDS troubleshooting scenarios.
Detailed technical explanation
The AWSServiceRoleForRDS service-linked role is a predefined IAM role that trusts the rds.amazonaws.com service and includes the AWS managed policy AmazonRDSEncryptionKeyAccess, which grants permissions to decrypt and re-encrypt KMS keys. When you launch an encrypted RDS instance, RDS assumes this role to call KMS APIs like Decrypt and GenerateDataKey; if the role is missing, the API call fails with an access denied error. In practice, this role is often deleted accidentally during account cleanup, and recreating it via the IAM console or AWS CLI (using create-service-linked-role) resolves the issue without modifying key policies.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Data Protection — This question tests Data Protection — Read the scenario before looking for a memorised answer..
The correct answer is: The AWSServiceRoleForRDS service-linked role is missing — The AWSServiceRoleForRDS service-linked role is required for RDS to call AWS KMS on your behalf to manage encryption keys for encrypted DB instances. If this role is missing, RDS cannot obtain the necessary permissions to decrypt the KMS key during instance launch, resulting in a KMS access error. This role is automatically created the first time you create an RDS resource, but if it was deleted or not present, you must recreate it to resolve the issue.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This SCS-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SCS-C02 exam.
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