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Question 252 of 1,730

Monitoring and Troubleshooting →hardMultiple ChoiceObjective-mapped

DynamoDB On-Demand Throttling: Hot Partition Troubleshooting

This DBS-C01 practice question tests your understanding of monitoring and troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: hot Partition. 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 using Amazon DynamoDB as the primary database for a global e-commerce application. During the holiday season, the application experiences throttling on write requests even though the read and write capacity units are well below the provisioned limits. The table uses on-demand capacity mode. What is the most likely cause of this throttling?

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.
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
There is a hot partition due to an uneven write distribution across partition keys.
Correct. Uneven write distribution creates a hot partition that exceeds the partition's throughput limit, causing throttling even in on-demand mode.
B
The table's provisioned write capacity is set too low.
Why wrong: Incorrect. The table uses on-demand capacity mode, so there is no provisioned write capacity to set too low.
C
The table has exceeded the maximum write capacity units per partition.
Why wrong: Incorrect. While each partition has a maximum capacity (1,000 WCU), this option inaccurately describes the issue as a table-level limit rather than a single partition limitation.
D
The AWS account has reached the DynamoDB write throughput limit per region.
Why wrong: Incorrect. AWS accounts do not have a regional write throughput limit for DynamoDB that would throttle a single table.

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

✓

There is a hot partition due to an uneven write distribution across partition keys.

In DynamoDB on-demand capacity mode, throughput scales automatically based on traffic. However, throttling can still occur if a single partition receives more write requests than the partition's maximum throughput capacity (1,000 WCU per partition). This is known as a hot partition, caused by an uneven distribution of write activity across partition keys. Option A correctly identifies this. Option B is incorrect because on-demand mode does not use provisioned capacity. Option C uses incorrect terminology—there is no 'maximum write capacity units per partition' that the table as a whole can exceed. Option D is incorrect because DynamoDB does not have a per-region account-level write limit that causes throttling on a single table.

Key principle: Hot Partition

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
There is a hot partition due to an uneven write distribution across partition keys.
Why this is correct
Correct. Uneven write distribution creates a hot partition that exceeds the partition's throughput limit, causing throttling even in on-demand mode.
Clue confirmation
The clue words "most likely", "primary" in the question point toward this answer.
Related concept
Hot Partition
✗
The table's provisioned write capacity is set too low.
Why it's wrong here
Incorrect. The table uses on-demand capacity mode, so there is no provisioned write capacity to set too low.
✗
The table has exceeded the maximum write capacity units per partition.
Why it's wrong here
Incorrect. While each partition has a maximum capacity (1,000 WCU), this option inaccurately describes the issue as a table-level limit rather than a single partition limitation.
✗
The AWS account has reached the DynamoDB write throughput limit per region.
Why it's wrong here
Incorrect. AWS accounts do not have a regional write throughput limit for DynamoDB that would throttle a single table.

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

Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.

KKey Concepts to Remember

Hot Partition
Partition Key Design
On-Demand Capacity Mode

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

Hot Partition

Real-world example

How this comes up in practice

An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.

What to study next

Got this wrong? Here's your next step.

Review hot Partition, then practise related DBS-C01 questions on the same topic to reinforce the concept.

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FAQ

Questions learners often ask

What does this DBS-C01 question test?

Monitoring and Troubleshooting — This question tests Monitoring and Troubleshooting — Hot Partition.

What is the correct answer to this question?

The correct answer is: There is a hot partition due to an uneven write distribution across partition keys. — In DynamoDB on-demand capacity mode, throughput scales automatically based on traffic. However, throttling can still occur if a single partition receives more write requests than the partition's maximum throughput capacity (1,000 WCU per partition). This is known as a hot partition, caused by an uneven distribution of write activity across partition keys. Option A correctly identifies this. Option B is incorrect because on-demand mode does not use provisioned capacity. Option C uses incorrect terminology—there is no 'maximum write capacity units per partition' that the table as a whole can exceed. Option D is incorrect because DynamoDB does not have a per-region account-level write limit that causes throttling on a single table.

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

Review hot Partition, then practise related DBS-C01 questions on the same topic to reinforce the concept.

Are there clue words in this question I should notice?

Yes — watch for: "most likely", "primary". 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?

Hot Partition

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Same concept, more angles

1 more ways this is tested on DBS-C01

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. An organization is using Amazon DynamoDB with on-demand capacity. They notice that the 'ThrottledRequests' metric is non-zero during a specific hour each day. The table stores session data and has a partition key of 'user_id'. The workload is uniform. What is the most likely cause of throttling?

medium

A.The table has on-demand capacity and cannot throttle.
✓ B.The account-level read/write capacity limit is exceeded.
C.A global secondary index is consuming write capacity.
D.The partition key is not evenly distributed.

Why B: Option B is correct because with on-demand capacity, throttling can occur when the account-level read/write capacity limit is exceeded, even with a uniform workload. The account-level limit (default 40,000 RCU or 40,000 WCU) applies across all on-demand tables in an AWS account. If the workload spikes during a specific hour, it may exceed this limit, causing throttling. Although per-partition limits exist (3,000 RCU or 1,000 WCU), a uniform workload means partition key distribution is even, so hot partitions are unlikely. Thus, the most likely cause is the account-level limit being reached.

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