The answer is that the application is using a service account that is not present in the AWS Managed AD. This is the most likely cause of the authentication failure because while the on-premises AD and AWS Managed AD are synchronized for user objects, service accounts used by the .NET application for Windows authentication are often not replicated or are configured with different credentials. The EC2 instances are domain-joined, so DNS and network connectivity are functional, but the application’s configured service account must exist in the local AWS Managed AD domain with the correct permissions to authenticate. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of the boundary between directory synchronization and application-level identity configuration—a common trap is assuming sync covers all objects, including service accounts. Remember the mnemonic: “Sync users, not service accounts” to avoid this pitfall when diagnosing AWS Managed AD authentication failures.
SAP-C02 Practice Question: Accelerate Workload Migration and Modernization
This SAP-C02 practice question tests your understanding of accelerate workload migration and modernization. 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 company is migrating a large .NET application to AWS. The application uses Windows authentication and integrates with Active Directory. The company wants to minimize operational overhead for the directory service. The on-premises Active Directory is already synchronized to AWS using AWS Directory Service for Microsoft Active Directory. During migration, the application fails to authenticate users. The security team confirms that the on-premises AD and AWS Managed AD are in sync. The application is running on EC2 instances that are joined to the AWS Managed AD domain. The application logs show authentication errors. What is the most likely cause of the authentication failure?
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.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The application is using a service account that is not in the AWS Managed AD.
When using AWS Managed AD, the EC2 instances need to be joined to the domain. However, the application's service account or configuration must be properly set up. The most common issue is that the application is using the wrong domain credentials or the service account does not have the necessary permissions. Option A is wrong because if instances are domain-joined, they can resolve DNS. Option B is wrong because the firewall rules are for network access, not authentication. Option D is wrong because NTLM is enabled by default.
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.
✗
The application requires NTLM authentication, which is disabled by default.
The application is using a service account that is not in the AWS Managed AD.
Why this is correct
Common cause: service account not migrated or created.
Clue confirmation
The clue words "most likely", "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 SAP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Accelerate Workload Migration and Modernization — This question tests Accelerate Workload Migration and Modernization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The application is using a service account that is not in the AWS Managed AD. — When using AWS Managed AD, the EC2 instances need to be joined to the domain. However, the application's service account or configuration must be properly set up. The most common issue is that the application is using the wrong domain credentials or the service account does not have the necessary permissions. Option A is wrong because if instances are domain-joined, they can resolve DNS. Option B is wrong because the firewall rules are for network access, not authentication. Option D is wrong because NTLM is enabled by default.
What should I do if I get this SAP-C02 question wrong?
Identify which SAP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely", "minimum / minimize". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 →
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 company is migrating a legacy .NET application to AWS. The application uses Windows authentication and integrates with on-premises Active Directory. The company wants to use AWS Managed Microsoft AD to reduce administrative overhead. However, after migration, the application fails to authenticate users. What is the most likely cause?
hard
A.The security group for the application servers does not allow inbound traffic on port 389.
B.AWS Managed Microsoft AD does not support LDAP queries.
C.The application is not configured to use the correct DNS servers for the AWS Managed Microsoft AD domain.
✓ D.The application is using NTLM authentication, which is not supported by AWS Managed Microsoft AD without a trust relationship.
Why D: Option D is correct because the application likely uses NTLM or Kerberos authentication, which requires proper trust relationships between the AWS Managed Microsoft AD and the on-premises AD. Option A is wrong because security groups do not affect authentication protocols. Option B is wrong because AWS Managed Microsoft AD supports LDAP. Option C is wrong because DNS resolution is not the root cause.
Last reviewed: Jun 20, 2026
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This SAP-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 SAP-C02 exam.
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