SCS-C02 Identity and Access Management Practice Question
Which THREE factors should be considered when designing IAM policies for cross-account access? (Choose three.)
⚠ Common exam trap
The SCS-C02 exam often tests the misconception that only one policy (either resource-based or identity-based) is sufficient for cross-account access, but in reality both the resource-based policy and the external account's IAM policy must allow the action.
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
✓
The resource-based policy must allow the external account
For cross-account access using resource-based policies (e.g., S3 bucket policies, KMS key policies), the resource-based policy must explicitly grant access to the external AWS account. This allows the external account's IAM principals to access the resource, provided the external account's IAM policy also permits the action. Without this allowance in the resource-based policy, the external account cannot access the resource, even if its own IAM policies allow it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The resource-based policy must allow the external account
Why this is correct
For cross-account access, the resource owner must explicitly grant the external account or its principal access in the resource-based policy. This policy defines the trust relationship because it specifies who can access the resource and what actions they can perform. Without this allow, the request fails even if the caller has valid IAM permissions in their own account.
- ✗
Permission boundaries must be used
Why it's wrong here
Permission boundaries are an optional IAM feature that sets the maximum permissions an entity can receive, but they are not a required part of IAM design. You only need them if you have a delegation model or want to cap privileges for specific roles or users. Standard IAM design can be fully functional without using permission boundaries, so they cannot be a mandatory design factor.
- ✓
The AWS account ID must be specified in the policy
Why this is correct
In a cross-account resource policy, you must identify the trusting party by specifying the external AWS account ID as part of the principal or condition. This account ID is what tells IAM that a principal from that account is allowed to access the resource. Without it, the policy would not recognize the external account, and the resource-based allow would not apply to that account.
- ✓
The IAM policy in the external account must allow the action
Why this is correct
The identity-based IAM policy attached to the external account's user or role must explicitly allow the action being attempted. Cross-account authorization is conjunctive: the resource-based policy grants permission to the account, but the principal's own IAM policy must also contain a matching allow. This requirement prevents a resource owner from simply handing out access to principals who would otherwise be restricted by their own account.
- ✗
Service control policies (SCPs) must allow the action
Why it's wrong here
Service control policies apply only within AWS Organizations to set account-wide guardrails, and they never grant permissions by themselves. When designing cross-account access via a resource-based policy, the presence or absence of an SCP is not a design consideration because SCPs can only deny or restrict already-granted permissions. Additionally, many AWS accounts exist outside an organization, so SCPs cannot be a universal factor in IAM design.
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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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.