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Management and Operations →hardMultiple ChoiceObjective-mapped

DocumentDB Sharding for Write Latency

This DBS-C01 practice question tests your understanding of management and operations. 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 logistics company operates a fleet tracking system using Amazon DocumentDB (with MongoDB compatibility). The database stores location updates from thousands of vehicles every second. The collection has a compound index on (vehicle_id, timestamp). Recently, the company noticed that write latency has increased, and the primary instance's CPU is consistently above 80%. The storage is gp2, and the instance is a db.r5.large. The operations team suspects that index maintenance is causing high CPU. The database administrator needs to reduce write latency without sacrificing query performance for real-time location queries. What should the administrator do?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.

A
Remove the compound index and rely on the default _id index for queries.
Why wrong: Option A is wrong because removing the compound index would harm query performance, especially for the real-time location queries that rely on filtering by vehicle_id and timestamp.
B
Upgrade to a larger instance class, such as db.r5.xlarge, to provide more CPU and memory.
Why wrong: Increasing instance size adds CPU but does not address the root cause of index maintenance overhead.
C
Disable journaling to reduce write I/O.
Why wrong: Option C is wrong because disabling journaling reduces write durability, not index maintenance overhead. It does not address the CPU issue and risks data loss.
D
Shard the collection using a hash-based shard key on vehicle_id to distribute write load.
Sharding the collection using a hash-based shard key on vehicle_id distributes writes evenly and reduces index maintenance overhead.

Full breakdown with real-world context →

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

✓

Shard the collection using a hash-based shard key on vehicle_id to distribute write load.

Option D is correct because sharding the collection using a hash-based shard key on vehicle_id distributes writes evenly and reduces index maintenance overhead. Option A is wrong because removing the compound index harms query performance for real-time location queries. Option B is wrong because upgrading to a larger instance class adds CPU but does not address the root cause of index maintenance overhead. Option C is wrong because disabling journaling reduces durability, not index maintenance.

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.

✗
Remove the compound index and rely on the default _id index for queries.
Why it's wrong here
Option A is wrong because removing the compound index would harm query performance, especially for the real-time location queries that rely on filtering by vehicle_id and timestamp.
✗
Upgrade to a larger instance class, such as db.r5.xlarge, to provide more CPU and memory.
Why it's wrong here
Increasing instance size adds CPU but does not address the root cause of index maintenance overhead.
✗
Disable journaling to reduce write I/O.
Why it's wrong here
Option C is wrong because disabling journaling reduces write durability, not index maintenance overhead. It does not address the CPU issue and risks data loss.
✓
Shard the collection using a hash-based shard key on vehicle_id to distribute write load.
Why this is correct
Sharding the collection using a hash-based shard key on vehicle_id distributes writes evenly and reduces index maintenance overhead.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.

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 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.

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Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

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FAQ

Questions learners often ask

What does this DBS-C01 question test?

Management and Operations — This question tests Management and Operations — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Shard the collection using a hash-based shard key on vehicle_id to distribute write load. — Option D is correct because sharding the collection using a hash-based shard key on vehicle_id distributes writes evenly and reduces index maintenance overhead. Option A is wrong because removing the compound index harms query performance for real-time location queries. Option B is wrong because upgrading to a larger instance class adds CPU but does not address the root cause of index maintenance overhead. Option C is wrong because disabling journaling reduces durability, not index maintenance.

What should I do if I get this DBS-C01 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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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.