The answer is to create a materialized view that stores daily sales aggregates and refresh it nightly. This is the most cost-effective solution because a materialized view pre-computes and stores the aggregated result set, eliminating the need to scan the full 500-million-row orders table at query time. By refreshing the view nightly, the report query reads only the small, pre-aggregated data, reducing execution time from 15 minutes to under 30 seconds without expensive infrastructure changes. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of when to use materialized views versus indexes, partitioning, or instance scaling for materialized view query performance. A common trap is choosing an index on the date column, which still requires scanning large row ranges, or partitioning, which only limits scan scope to a single partition. Remember the mnemonic: “Pre-aggregate, don’t scan—materialized views are the plan.”
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.
An e-commerce platform uses Amazon RDS for PostgreSQL to store order data. The database has a table "orders" with 500 million rows. The application runs a report query that aggregates daily sales for the last 30 days. The query currently scans the entire table and takes 15 minutes to complete. The team needs to reduce the query time to under 30 seconds. Which solution is MOST cost-effective?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a materialized view that stores daily sales aggregates and refresh it nightly.
Option B is correct because a materialized view can pre-aggregate the daily sales, and refreshing it daily avoids scanning the full table. Option A is wrong because indexes on date columns help but still require scanning large portions. Option C is wrong because partitioning by month still requires scanning the partition. Option D is wrong because upgrading to a larger instance is costly and may not achieve sub-30 seconds.
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.
✗
Partition the table by month and query only the relevant partitions.
Why it's wrong here
Partition pruning helps but still requires scanning 30 days of data (one partition). Aggregation over that partition can be slow.
✓
Create a materialized view that stores daily sales aggregates and refresh it nightly.
Why this is correct
The report reads pre-computed aggregates, reducing query time drastically.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a composite index on the date column and the sales amount column.
Why it's wrong here
An index could help range scans but the query still needs to aggregate many rows, possibly still slow.
✗
Upgrade the RDS instance to a larger size with more vCPUs and memory.
Why it's wrong here
Scaling up is expensive and may not reduce query time to under 30 seconds due to full table scan.
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 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
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.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a materialized view that stores daily sales aggregates and refresh it nightly. — Option B is correct because a materialized view can pre-aggregate the daily sales, and refreshing it daily avoids scanning the full table. Option A is wrong because indexes on date columns help but still require scanning large portions. Option C is wrong because partitioning by month still requires scanning the partition. Option D is wrong because upgrading to a larger instance is costly and may not achieve sub-30 seconds.
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.
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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