The answer is to check the session table's storage engine and change it from MEMORY to InnoDB. This is correct because the MEMORY storage engine stores table data entirely in RAM, meaning any database restart, failover, or maintenance event—such as the CPU spikes indicating a restart—will wipe the session data, causing users to be logged out. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how RDS storage engines interact with application state, often trapping developers who assume all tables persist across restarts. A common mistake is to blame RDS Proxy or binary logs, but those handle connection pooling and replication, not table durability. Remember the memory tip: "MEMORY is volatile, InnoDB is durable"—if your session table uses MEMORY, a single RDS reboot will flush all active sessions.
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. 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 runs a web application on EC2 instances behind an Application Load Balancer (ALB). The application stores session data in an RDS MySQL database. Recently, users have reported that they are being logged out unexpectedly and their session data is lost. The developer investigates and finds that the RDS instance's CPU utilization spikes periodically, coinciding with the logout events. The application uses connection pooling via an RDS Proxy. The developer suspects that the session table is being dropped or truncated. After checking the application logs, the developer finds no evidence of truncation commands. The RDS instance has automated backups enabled, and the binary logs are retained for 24 hours. The developer wants to identify the root cause and prevent future occurrences. Which course of action should the developer take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the session table's storage engine; if it uses MEMORY, change it to InnoDB to persist data across restarts.
The RDS CPU spikes and session loss suggest that the database is being restarted or failing over, causing in-memory session data to be lost. However, the session data is stored in a table, which should survive restarts. The issue might be that the session table is using the MEMORY storage engine, which loses data on restart. Option C is correct: checking the table storage engine. Option A is wrong because RDS Proxy does not cause data loss. Option B is wrong because binary logs are for replication, not session persistence. Option D is wrong because increasing instance size may delay but not prevent the issue.
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.
✗
Enable Multi-AZ deployment for RDS to improve availability and prevent data loss during failover.
Why it's wrong here
Multi-AZ provides failover, but the session table may still lose data if it's not using a durable engine.
✗
Increase the RDS instance size to handle the CPU spikes and prevent future issues.
Why it's wrong here
Scaling up may reduce CPU spikes but does not address the root cause of data loss.
✗
Disable RDS Proxy and implement connection pooling in the application code to reduce database load.
Why it's wrong here
RDS Proxy is not the cause; it helps manage connections.
✓
Check the session table's storage engine; if it uses MEMORY, change it to InnoDB to persist data across restarts.
Why this is correct
MEMORY engine loses data on restart; InnoDB is durable.
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 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.
Identify which DVA-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.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Check the session table's storage engine; if it uses MEMORY, change it to InnoDB to persist data across restarts. — The RDS CPU spikes and session loss suggest that the database is being restarted or failing over, causing in-memory session data to be lost. However, the session data is stored in a table, which should survive restarts. The issue might be that the session table is using the MEMORY storage engine, which loses data on restart. Option C is correct: checking the table storage engine. Option A is wrong because RDS Proxy does not cause data loss. Option B is wrong because binary logs are for replication, not session persistence. Option D is wrong because increasing instance size may delay but not prevent the issue.
What should I do if I get this DVA-C02 question wrong?
Identify which DVA-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.
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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