This DBS-C01 practice question tests your understanding of workload-specific database design. 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.
A company is using Amazon DynamoDB to store session data for a web application. The session data expires after 24 hours. Which DynamoDB feature should the company use to automatically delete expired items?
A retention policy on the DynamoDB table
Why wrong: DynamoDB does not have a built-in retention policy.
DynamoDB Time to Live (TTL)
TTL automatically deletes expired items based on a timestamp attribute.
DynamoDB Streams
Why wrong: Streams capture changes but do not delete items.
A scheduled AWS Lambda function that scans and deletes expired items
Why wrong: More complex and costly; TTL is simpler.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DynamoDB Time to Live (TTL)
DynamoDB Time to Live (TTL) is the correct choice because it provides a cost-effective, fully managed mechanism to automatically delete expired items based on a timestamp attribute in the table. TTL works by comparing the current time to the epoch time value stored in the designated TTL attribute; when the value is in the past, DynamoDB marks the item for deletion, typically within 48 hours. This eliminates the need for custom code or additional AWS services, directly addressing the requirement to remove session data after 24 hours.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
A retention policy on the DynamoDB table
Why it's wrong here
DynamoDB does not have a built-in retention policy.
DynamoDB Time to Live (TTL)
Why this is correct
TTL automatically deletes expired items based on a timestamp attribute.
Related concept
Read the scenario before looking for a memorised answer.
DynamoDB Streams
Why it's wrong here
Streams capture changes but do not delete items.
A scheduled AWS Lambda function that scans and deletes expired items
Why it's wrong here
More complex and costly; TTL is simpler.
Common exam traps
The trap here is that candidates may overcomplicate the solution by choosing a custom Lambda-based approach (Option D) or misidentifying Streams (Option C) as a deletion mechanism, when DynamoDB's native TTL feature is the simplest, most cost-effective, and fully managed answer.
Detailed technical explanation
Under the hood, DynamoDB TTL uses a background process that continuously scans table partitions for expired items; once an item's TTL attribute timestamp is past, it is marked for deletion, and the actual deletion occurs asynchronously, typically within 48 hours but often much sooner. A subtle behavior is that TTL does not guarantee immediate deletion at the exact expiry time; for session data that must be removed promptly for compliance or security, you may need to combine TTL with a filter expression in queries to exclude expired items from read results. In real-world scenarios, TTL is ideal for session stores, log entries, and time-series data where eventual deletion is acceptable, reducing storage costs without manual intervention.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
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FAQ
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
The correct answer is: DynamoDB Time to Live (TTL) — DynamoDB Time to Live (TTL) is the correct choice because it provides a cost-effective, fully managed mechanism to automatically delete expired items based on a timestamp attribute in the table. TTL works by comparing the current time to the epoch time value stored in the designated TTL attribute; when the value is in the past, DynamoDB marks the item for deletion, typically within 48 hours. This eliminates the need for custom code or additional AWS services, directly addressing the requirement to remove session data after 24 hours.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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