- A
Increase storage to 500 GB
Why wrong: Storage scaling does not directly improve write latency; DocumentDB storage is automatically scaled.
- B
Enable Multi-AZ deployment
Why wrong: Multi-AZ provides high availability but does not improve write performance.
- C
Increase the instance size to db.r5.xlarge
A larger instance provides more CPU and memory, which can improve write performance.
- D
Add a read replica in a different Availability Zone
Why wrong: Read replicas handle read traffic only, not writes.
Question 889 of 1,730
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 company is running a MongoDB-compatible workload on Amazon DocumentDB. They are experiencing high write latency during peak hours. The current cluster has one instance (db.r5.large) with 100 GB storage. Which change is most likely to improve write performance?
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 choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the instance size to db.r5.xlarge
Increasing the instance size to db.r5.xlarge provides more CPU and memory resources, which directly improves the cluster's ability to handle write operations under load. In Amazon DocumentDB, write performance is primarily bound by the instance's compute capacity (vCPUs and memory) for processing write requests and managing the storage engine's buffer cache. A larger instance reduces contention and allows more concurrent writes to be processed efficiently.
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.
- ✗
Increase storage to 500 GB
Why it's wrong here
Storage scaling does not directly improve write latency; DocumentDB storage is automatically scaled.
- ✗
Enable Multi-AZ deployment
Why it's wrong here
Multi-AZ provides high availability but does not improve write performance.
- ✓
Increase the instance size to db.r5.xlarge
Why this is correct
A larger instance provides more CPU and memory, which can improve write performance.
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.
- ✗
Add a read replica in a different Availability Zone
Why it's wrong here
Read replicas handle read traffic only, not writes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume increasing storage or adding read replicas will improve write performance, but in DocumentDB, write throughput is limited by the primary instance's compute resources, not by storage size or read capacity.
Detailed technical explanation
How to think about this question
Amazon DocumentDB uses a shared storage volume that automatically scales up to 64 TB, so storage size does not limit write performance. Write I/O is governed by the instance's ability to process operations and by the DocumentDB storage subsystem's I/O credit mechanism, which is tied to instance size. In practice, a db.r5.large has 2 vCPUs and 16 GiB memory, while a db.r5.xlarge doubles both to 4 vCPUs and 32 GiB, providing more parallelism for write-intensive workloads like bulk inserts or high-frequency updates.
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.
TExam Day Tips
- 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.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
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: Increase the instance size to db.r5.xlarge — Increasing the instance size to db.r5.xlarge provides more CPU and memory resources, which directly improves the cluster's ability to handle write operations under load. In Amazon DocumentDB, write performance is primarily bound by the instance's compute capacity (vCPUs and memory) for processing write requests and managing the storage engine's buffer cache. A larger instance reduces contention and allows more concurrent writes to be processed efficiently.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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Last reviewed: Jul 4, 2026
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