DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 social media application uses Amazon DynamoDB with a table that has a partition key of 'user_id' and a sort key of 'post_timestamp'. The application frequently queries for the 10 most recent posts by a specific user. The query pattern uses a 'begins_with' condition on the sort key with a timestamp prefix. Recently, the query latency has increased significantly for users with many posts. Which design change would improve query performance?
Create a local secondary index (LSI) with 'user_id' as partition key and 'post_timestamp' as sort key, and query using reverse order with a limit of 10.
LSI allows efficient query for most recent posts by user without scanning all posts.
B
Enable DynamoDB Accelerator (DAX) to cache the query results.
Why wrong: DAX reduces latency but does not reduce the read capacity consumed; underlying query still scans.
C
Create a global secondary index (GSI) with 'post_timestamp' as partition key and 'user_id' as sort key.
Why wrong: This reverses the keys; querying by user_id would still require a scan.
D
Change the table's partition key to 'post_id' to distribute data more evenly.
Why wrong: Does not help querying by user; would require full table scan.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a local secondary index (LSI) with 'user_id' as partition key and 'post_timestamp' as sort key, and query using reverse order with a limit of 10.
Option D is correct because creating a secondary index with 'user_id' as partition key and 'post_timestamp' as sort key, and using a 'Query' with reverse order and limit 10, avoids scanning all posts. Option A is wrong because a global secondary index still requires scanning if not optimized. Option B is wrong because changing partition key to 'post_id' would break the query pattern. Option C is wrong because DynamoDB Accelerator (DAX) caches results but doesn't reduce the read capacity consumed per query; the query still scans all items for a user.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Create a local secondary index (LSI) with 'user_id' as partition key and 'post_timestamp' as sort key, and query using reverse order with a limit of 10.
Why this is correct
LSI allows efficient query for most recent posts by user without scanning all posts.
Related concept
Static NAT maps one inside address to one outside address.
✗
Enable DynamoDB Accelerator (DAX) to cache the query results.
Why it's wrong here
DAX reduces latency but does not reduce the read capacity consumed; underlying query still scans.
✗
Create a global secondary index (GSI) with 'post_timestamp' as partition key and 'user_id' as sort key.
Why it's wrong here
This reverses the keys; querying by user_id would still require a scan.
✗
Change the table's partition key to 'post_id' to distribute data more evenly.
Why it's wrong here
Does not help querying by user; would require full table scan.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DBS-C01 NAT questions on configuration and troubleshooting.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create a local secondary index (LSI) with 'user_id' as partition key and 'post_timestamp' as sort key, and query using reverse order with a limit of 10. — Option D is correct because creating a secondary index with 'user_id' as partition key and 'post_timestamp' as sort key, and using a 'Query' with reverse order and limit 10, avoids scanning all posts. Option A is wrong because a global secondary index still requires scanning if not optimized. Option B is wrong because changing partition key to 'post_id' would break the query pattern. Option C is wrong because DynamoDB Accelerator (DAX) caches results but doesn't reduce the read capacity consumed per query; the query still scans all items for a user.
What should I do if I get this DBS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DBS-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This DBS-C01 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 DBS-C01 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.