The answer is that the user 'app_user' does not have access from host '10.0.1.50'. This is the most likely cause because MySQL enforces host-based access control by defining user accounts as 'user'@'host', and when the application connects from an IP address not included in the user's allowed hosts, MySQL rejects the connection with an authentication failure even when the password is correct. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of how RDS MySQL authentication failures due to host restrictions differ from password errors, often appearing as a trap where engineers mistakenly reset credentials. The key insight is that the error logs show repeated failures despite a valid password, pointing directly to a host mismatch rather than a credential issue. Memory tip: think of it as a bouncer checking both your ID (password) and your guest list (host)—if your name isn't on the list for that specific door, you don't get in.
DBS-C01 Monitoring and Troubleshooting Practice Question
This DBS-C01 practice question tests your understanding of monitoring and troubleshooting. 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.
Exhibit
Refer to the exhibit.
From Amazon CloudWatch Logs:
2023-04-01T12:00:00Z [ERROR] [Client] Authentication failed for user 'app_user' from host '10.0.1.50' using method 'mysql_native_password'
2023-04-01T12:01:00Z [ERROR] [Client] Access denied for user 'app_user'@'10.0.1.50' (using password: YES)
2023-04-01T12:02:00Z [ERROR] [Client] Access denied for user 'app_user'@'10.0.1.50' (using password: YES)
A database engineer is reviewing Amazon RDS for MySQL error logs and sees repeated authentication failures from the same IP address. The application team confirms the password is correct. What is the most likely cause of these errors?
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.
Refer to the exhibit.
From Amazon CloudWatch Logs:
2023-04-01T12:00:00Z [ERROR] [Client] Authentication failed for user 'app_user' from host '10.0.1.50' using method 'mysql_native_password'
2023-04-01T12:01:00Z [ERROR] [Client] Access denied for user 'app_user'@'10.0.1.50' (using password: YES)
2023-04-01T12:02:00Z [ERROR] [Client] Access denied for user 'app_user'@'10.0.1.50' (using password: YES)
A
The password is incorrect
Why wrong: The application team confirmed the password is correct.
B
The user 'app_user' does not have access from host '10.0.1.50'
The user may be defined as 'app_user'@'%' or from a different host, causing a mismatch.
C
The 'app_user' account is locked
Why wrong: A locked account would show a different error.
D
The database requires SSL connections
Why wrong: SSL requirement would show a different error.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The user 'app_user' does not have access from host '10.0.1.50'
The error logs show authentication failures despite the password being correct, which indicates the issue is not with the password itself but with the host-based access control. In MySQL, user accounts are defined as 'user'@'host', and if the application is connecting from an IP address (e.g., 10.0.1.50) that is not included in the user's allowed hosts, MySQL will reject the connection with an authentication error even if the password is correct. This is a common misconfiguration when migrating or scaling applications across different subnets.
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 password is incorrect
Why it's wrong here
The application team confirmed the password is correct.
✓
The user 'app_user' does not have access from host '10.0.1.50'
Why this is correct
The user may be defined as 'app_user'@'%' or from a different host, causing a mismatch.
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 trap: answer the scenario, not the keyword
The trap here is that candidates often assume authentication failures always mean a wrong password, but AWS/DBS-C01 tests your understanding that MySQL's host-based authentication can produce the same error message when the host is not authorized, even with a valid password.
Trap categories for this question
Command / output trap
A locked account would show a different error.
Detailed technical explanation
How to think about this question
MySQL's authentication model uses the `mysql.user` table where each user is identified by both username and host (e.g., 'app_user'@'10.0.1.%' or 'app_user'@'%'). When a connection request arrives, MySQL checks the host portion first; if the host does not match any entry for that user, it returns an 'Access denied' error without even checking the password. This behavior is defined in the MySQL protocol and can be verified by querying `SELECT user, host FROM mysql.user WHERE user = 'app_user';`. In Amazon RDS, you can modify host permissions using the `CALL mysql.rds_set_configuration` procedure or by creating a new user with the correct host mask.
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.
Monitoring and Troubleshooting — This question tests Monitoring and Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The user 'app_user' does not have access from host '10.0.1.50' — The error logs show authentication failures despite the password being correct, which indicates the issue is not with the password itself but with the host-based access control. In MySQL, user accounts are defined as 'user'@'host', and if the application is connecting from an IP address (e.g., 10.0.1.50) that is not included in the user's allowed hosts, MySQL will reject the connection with an authentication error even if the password is correct. This is a common misconfiguration when migrating or scaling applications across different subnets.
What should I do if I get this DBS-C01 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: "most likely". 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.
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Question Discussion
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