The answer is to change the trust policy principal from the account root to arn:aws:iam::222233334444:role/BatchRunner while keeping the ExternalId condition. This is correct because a cross-account role trust policy must explicitly define which identities can assume the role; using the account root ARN would allow any role in Account B to assume it, whereas specifying the exact role ARN restricts assumption to only that BatchRunner role. The ExternalId condition then acts as a shared secret, preventing any other role in Account B from reusing the same external ID even if they try to mimic the trust policy. On the SAA-C03 exam, this tests your understanding of least privilege in cross-account access and the common trap of using account root as a principal, which is overly permissive. Remember the memory tip: “Principal pinpoints, ExternalId prevents piggybacking”—the principal locks the door to the specific role, and the ExternalId ensures no other role can sneak through with the same key.
SAA-C03 Design Secure Architectures Practice Question
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. 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.
Based on the exhibit, a batch platform in Account B must assume a role in Account A. Only the specific role arn:aws:iam::222233334444:role/BatchRunner should be allowed to assume it, and the design must prevent any other role in Account B from reusing the same external ID. Which change best meets the requirement?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Add an identity-based policy to the BatchRunner role that allows sts:AssumeRole on the target role.
Why wrong: The caller still also needs the trust policy to allow the specific principal. Identity policy alone does not authorize cross-account role assumption.
B
Change the trust policy principal from account root to arn:aws:iam::222233334444:role/BatchRunner and keep the ExternalId condition.
This limits assumption to the exact role in Account B while preserving the ExternalId defense against confused deputy attacks.
C
Replace the ExternalId condition with a role session name condition so only BatchRunner sessions are accepted.
Why wrong: Role session names are not a strong security boundary and are easily chosen by the caller.
D
Attach an SCP to Account B that denies sts:AssumeRole unless the request comes from BatchRunner.
Why wrong: SCPs can restrict actions in Account B, but they do not replace the required trust policy in Account A.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the trust policy principal from account root to arn:aws:iam::222233334444:role/BatchRunner and keep the ExternalId condition.
Option B is correct because the trust policy on the target role in Account A must restrict the principal to the exact BatchRunner role ARN (arn:aws:iam::222233334444:role/BatchRunner) rather than the entire Account B root. This ensures that only that specific role can assume the target role. Keeping the ExternalId condition adds an additional layer of security by requiring a unique identifier that only BatchRunner knows, preventing any other role in Account B from reusing the same external ID.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Add an identity-based policy to the BatchRunner role that allows sts:AssumeRole on the target role.
Why it's wrong here
The caller still also needs the trust policy to allow the specific principal. Identity policy alone does not authorize cross-account role assumption.
✓
Change the trust policy principal from account root to arn:aws:iam::222233334444:role/BatchRunner and keep the ExternalId condition.
Why this is correct
This limits assumption to the exact role in Account B while preserving the ExternalId defense against confused deputy attacks.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Replace the ExternalId condition with a role session name condition so only BatchRunner sessions are accepted.
Why it's wrong here
Role session names are not a strong security boundary and are easily chosen by the caller.
✗
Attach an SCP to Account B that denies sts:AssumeRole unless the request comes from BatchRunner.
Why it's wrong here
SCPs can restrict actions in Account B, but they do not replace the required trust policy in Account A.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think an identity-based policy on the assuming role (Option A) is sufficient, but the trust policy on the target role must explicitly restrict the principal to the specific role ARN, not just the account root.
Detailed technical explanation
How to think about this question
The trust policy on the target role uses the Principal element to specify which AWS entity can assume the role. By default, setting the principal to an account root ARN (e.g., arn:aws:iam::222233334444:root) allows any IAM entity in that account to assume the role, provided they have sts:AssumeRole permissions. Restricting the principal to a specific role ARN ensures that only that role can assume the target role, and the ExternalId condition (aws:ExternalId) is a string that must match exactly, preventing confused deputy attacks and ensuring that only the intended external party (BatchRunner) can use the role.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change the trust policy principal from account root to arn:aws:iam::222233334444:role/BatchRunner and keep the ExternalId condition. — Option B is correct because the trust policy on the target role in Account A must restrict the principal to the exact BatchRunner role ARN (arn:aws:iam::222233334444:role/BatchRunner) rather than the entire Account B root. This ensures that only that specific role can assume the target role. Keeping the ExternalId condition adds an additional layer of security by requiring a unique identifier that only BatchRunner knows, preventing any other role in Account B from reusing the same external ID.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This SAA-C03 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 SAA-C03 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.