SAA-C03 Practice Question: S3 bucket policies grant cross-account access.
This SAA-C03 practice question tests your understanding of design secure architectures. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: s3 bucket policies grant cross-account access.. 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 partner company needs read-only access to reports in an S3 bucket for a financial reporting platform. The partner has its own AWS account. What is the most secure scalable access pattern?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a bucket policy that grants the partner role least-privilege access to the required prefix
Option A is correct because a bucket policy with a condition that grants read-only access to a specific prefix allows the partner's AWS account to access the S3 bucket without creating IAM users or sharing long-term credentials. This leverages cross-account IAM roles, where the partner assumes a role in their own account that the bucket policy trusts, ensuring least-privilege access and eliminating the need to manage static keys. The policy can be scoped to a specific prefix (e.g., `reports/`) and use the `aws:SourceArn` or `aws:SourceAccount` condition key to restrict access to only the partner's account, providing both security and scalability.
Key principle: S3 bucket policies grant cross-account access.
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 bucket policy that grants the partner role least-privilege access to the required prefix
Why this is correct
A resource policy can grant cross-account access to a specific external role and prefix.
Related concept
S3 bucket policies grant cross-account access.
✗
Create an IAM user in the company account and share the access keys
Why it's wrong here
Long-term shared credentials are less secure and harder to govern.
✗
Copy the objects to a public website bucket
Why it's wrong here
A public website bucket exposes data unnecessarily.
✗
Make the objects public and rely on difficult-to-guess object names
Why it's wrong here
Security through obscurity is not an access-control strategy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose Option B (sharing IAM user access keys) because it seems simpler, but the exam tests the principle of using cross-account IAM roles with bucket policies for secure, scalable, and auditable access without managing static credentials.
Detailed technical explanation
How to think about this question
Under the hood, cross-account access via bucket policies works by the partner account creating an IAM role with a trust policy that allows the company's bucket policy to grant access. The bucket policy uses the `Principal` element set to the partner's AWS account ID (e.g., `"Principal": {"AWS": "arn:aws:iam::PARTNER_ACCOUNT_ID:root"}`) and a `Condition` block with `StringEquals` on `s3:prefix` to restrict to a specific path. This avoids the need for IAM users or access keys, and the partner can assume the role using AWS STS (`AssumeRole`), which generates temporary credentials valid for up to 1 hour, automatically rotating them. A real-world scenario is a SaaS provider granting read-only access to billing reports for each customer account, where the bucket policy dynamically references each customer's account ID via a condition key like `aws:SourceAccount`.
KKey Concepts to Remember
S3 bucket policies grant cross-account access.
Access can be restricted to specific S3 prefixes.
IAM roles provide temporary, programmatic access.
Least privilege is enforced by specific S3 actions.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
S3 bucket policies grant cross-account access.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review s3 bucket policies grant cross-account access., then practise related SAA-C03 questions on the same topic to reinforce the concept.
Design Secure Architectures — This question tests Design Secure Architectures — S3 bucket policies grant cross-account access..
What is the correct answer to this question?
The correct answer is: Create a bucket policy that grants the partner role least-privilege access to the required prefix — Option A is correct because a bucket policy with a condition that grants read-only access to a specific prefix allows the partner's AWS account to access the S3 bucket without creating IAM users or sharing long-term credentials. This leverages cross-account IAM roles, where the partner assumes a role in their own account that the bucket policy trusts, ensuring least-privilege access and eliminating the need to manage static keys. The policy can be scoped to a specific prefix (e.g., `reports/`) and use the `aws:SourceArn` or `aws:SourceAccount` condition key to restrict access to only the partner's account, providing both security and scalability.
What should I do if I get this SAA-C03 question wrong?
Review s3 bucket policies grant cross-account access., then practise related SAA-C03 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
S3 bucket policies grant cross-account access.
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