The answer is high storage latency due to provisioned IOPS being fully utilized or EBS volume contention. This is correct because the CloudWatch metrics show a ReadLatency of 2.5 ms and WriteLatency of 5 ms on an RDS PostgreSQL instance with 5000 provisioned IOPS, where sub-millisecond latency is expected; when IOPS are fully consumed or the underlying EBS volume experiences contention, the storage layer cannot keep up, driving up latency even if the IOPS count itself is not exceeded. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your ability to distinguish between resource saturation and performance degradation—a common trap is to blame memory or connections when the real culprit is storage throttling. Remember that high read latency on RDS PostgreSQL often points to the I/O subsystem, not compute or memory, so always check the ReadLatency metric against your provisioned IOPS baseline. A useful memory tip: “Latency leaps when IOPS sleep”—if latency is high but IOPS are within limits, suspect contention or throttling at the EBS level.
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.
Exhibit
Refer to the exhibit.
```json
{
"MemoryReservation": {
"Value": 500
},
"MemoryUsage": {
"Value": 450
},
"ActiveTransactions": {
"Value": 20
},
"DatabaseConnections": {
"Value": 100
},
"ReadIOPS": {
"Value": 5000
},
"WriteIOPS": {
"Value": 2000
},
"ReadLatency": {
"Value": 2.5
},
"WriteLatency": {
"Value": 5.0
}
}
```
The exhibit shows CloudWatch metrics from an Amazon RDS for PostgreSQL instance (db.r5.large, 16 GB memory, 5000 provisioned IOPS). The application is experiencing slow query performance.
Refer to the exhibit. The exhibit shows CloudWatch metrics from an Amazon RDS for PostgreSQL instance. The application is experiencing slow query performance. Which 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
✓
High storage latency due to provisioned IOPS being fully utilized or EBS volume contention
Option A is correct because ReadLatency of 2.5 ms is high for a database with 5000 provisioned IOPS; typically sub-millisecond is expected. WriteLatency of 5 ms is also high. Memory usage is 450 MB out of 16 GB, so memory is fine. Connections (100) are moderate. IOPS (5000 read, 2000 write) are within limits but latency is high, indicating potential throttling or contention. Option B: connections are not high. Option C: memory is not pressured. Option D: CPU is not mentioned; high latency is often storage-related.
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.
✓
High storage latency due to provisioned IOPS being fully utilized or EBS volume contention
Why this is correct
Read/Write latency significantly above expected values for provisioned IOPS storage.
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.
✗
High CPU utilization due to complex queries
Why it's wrong here
CPU metrics not shown, but latency is more likely storage-related.
✗
Too many database connections causing context switching
Why it's wrong here
100 connections is not excessive for db.r5.large.
✗
Insufficient memory causing disk swaps
Why it's wrong here
Memory usage is 450 MB, far below 16 GB.
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.
Trap categories for this question
Command / output trap
CPU metrics not shown, but latency is more likely storage-related.
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 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: High storage latency due to provisioned IOPS being fully utilized or EBS volume contention — Option A is correct because ReadLatency of 2.5 ms is high for a database with 5000 provisioned IOPS; typically sub-millisecond is expected. WriteLatency of 5 ms is also high. Memory usage is 450 MB out of 16 GB, so memory is fine. Connections (100) are moderate. IOPS (5000 read, 2000 write) are within limits but latency is high, indicating potential throttling or contention. Option B: connections are not high. Option C: memory is not pressured. Option D: CPU is not mentioned; high latency is often storage-related.
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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