The answer is that the Lambda function does not re-establish the stream session after a failover event. This is the most likely cause because RDS Database Activity Streams use a persistent session between the database and the consumer; when a Multi-AZ failover occurs, the standby instance becomes the primary, but the existing stream session is invalidated and must be reconnected. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding of how failover handling impacts stream continuity—a common trap is assuming that network-level components like security groups or KMS keys cause the disruption, when in fact the stream session itself is ephemeral and requires the consumer to re-establish it after any failover. Remember: after failover, the endpoint stays the same, but the stream session does not—always code your Lambda to reconnect on failure.
DBS-C01 Database Security Practice Question
This DBS-C01 practice question tests your understanding of database security. 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 using Amazon RDS for SQL Server with Multi-AZ deployment. The security team requires that all database activity be monitored for suspicious queries. The database specialist enabled RDS Database Activity Streams and configured AWS Lambda to process the stream. However, the Lambda function fails to process some events when the database fails over to the standby instance. What is the most likely cause?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Lambda function does not re-establish the stream session after a failover event.
Option D is correct because after failover, the stream session may be interrupted and the application must reconnect. Option A is wrong because the KMS key is used for encryption, not for connectivity. Option B is wrong because the security group applies to the RDS endpoint, which remains the same after failover. Option C is wrong because the parameter group is applied to both instances.
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 security group does not allow the Lambda function to connect to the new primary instance.
Why it's wrong here
The endpoint remains the same after failover.
✓
The Lambda function does not re-establish the stream session after a failover event.
Why this is correct
Activity streams require reconnection after failover.
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.
✗
The parameter group for the standby instance does not have the activity stream enabled.
Why it's wrong here
Both instances share the same parameter group.
✗
The KMS key used to encrypt the activity stream is not available in the standby instance's Region.
Why it's wrong here
Both instances are in the same Region.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which DBS-C01 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.
Database Security — This question tests Database Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Lambda function does not re-establish the stream session after a failover event. — Option D is correct because after failover, the stream session may be interrupted and the application must reconnect. Option A is wrong because the KMS key is used for encryption, not for connectivity. Option B is wrong because the security group applies to the RDS endpoint, which remains the same after failover. Option C is wrong because the parameter group is applied to both instances.
What should I do if I get this DBS-C01 question wrong?
Identify which DBS-C01 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". 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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