The correct answer is that the partition key is not evenly distributed, causing a hot partition. Even with DynamoDB on-demand throttling, each partition is still capped at 1,000 write capacity units or 3,000 read capacity units per second; when a single user_id receives a disproportionate share of traffic during that peak hour, it exceeds this per-partition limit, resulting in throttled requests despite the table’s overall on-demand capacity being sufficient. This question tests your understanding that on-demand mode does not eliminate partition-level constraints—a common trap on the AWS Certified Database Specialty DBS-C01 exam where candidates mistakenly assume on-demand means unlimited throughput. The key insight is that uniform workload distribution across partitions is critical; a skewed partition key like user_id can create a hot key even with uniform traffic patterns. Memory tip: think “partition ceiling, not table ceiling”—on-demand scales the table, but each partition still has its own glass ceiling.
DBS-C01 Monitoring and Troubleshooting Practice Question
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. 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 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?
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
✓
The partition key is not evenly distributed.
Option D is correct because the 'ThrottledRequests' metric indicates that requests are being throttled due to partition-level capacity limits. Even with on-demand capacity, DynamoDB imposes a per-partition throughput limit (typically 1,000 WCU or 3,000 RCU per partition). If the partition key 'user_id' is not evenly distributed, a single partition can become a hot key, exceeding its limit and causing throttling despite the table having on-demand capacity.
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.
✗
The table has on-demand capacity and cannot throttle.
Why it's wrong here
On-demand tables can still throttle due to per-partition throughput limits.
✗
The account-level read/write capacity limit is exceeded.
Why it's wrong here
On-demand capacity can burst beyond provisioned limits, but account limits are high.
✗
A global secondary index is consuming write capacity.
Why it's wrong here
If no GSI exists, this is not a factor.
✓
The partition key is not evenly distributed.
Why this is correct
Uneven access pattern can cause a hot partition leading to throttling even on on-demand tables.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume on-demand capacity eliminates all throttling, but DynamoDB still throttles at the partition level when a hot key causes uneven distribution, even with on-demand mode.
Detailed technical explanation
How to think about this question
DynamoDB on-demand capacity automatically scales to handle traffic, but it still enforces a per-partition throughput limit of 1,000 WCU or 3,000 RCU. When a single partition key value (e.g., a popular 'user_id') receives a disproportionate number of requests, that partition can hit its limit, causing throttling even if the overall table capacity is sufficient. This is a common scenario with session data if the partition key is not designed to distribute load evenly, such as using a sequential user ID that creates a hot partition during peak hours.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Monitoring and Troubleshooting — This question tests Monitoring and Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The partition key is not evenly distributed. — Option D is correct because the 'ThrottledRequests' metric indicates that requests are being throttled due to partition-level capacity limits. Even with on-demand capacity, DynamoDB imposes a per-partition throughput limit (typically 1,000 WCU or 3,000 RCU per partition). If the partition key 'user_id' is not evenly distributed, a single partition can become a hot key, exceeding its limit and causing throttling despite the table having on-demand capacity.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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. 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?
hard
✓ A.There is a hot partition due to an uneven write distribution across partition keys.
B.The table's provisioned write capacity is set too low.
C.The table has exceeded the maximum write capacity units per partition.
D.The AWS account has reached the DynamoDB write throughput limit per region.
Why A: Option D is correct because on-demand capacity mode automatically scales but can throttle if traffic is unevenly distributed across partitions, leading to hot partitions. Option A is incorrect because on-demand mode does not have a per-table limit in the same way provisioned capacity does. Option B is incorrect because DynamoDB does not have a global write limit per account that would cause throttling on a single table. Option C is incorrect because the table uses on-demand capacity mode, not provisioned.
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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.
Question Discussion
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