- A
The function is writing to a single partition key, causing hot partition throttling
Correct. Hot partitions can cause throttling even when table-level capacity is sufficient. The function's writes are likely concentrated on one partition key, exceeding that partition's throughput limits.
- B
The function's reserved concurrency is too high, causing excessive write requests
Why wrong: Incorrect. With 10 WCUs per invocation and concurrency 10, maximum table usage is 100 WCUs, well below the provisioned 500 WCUs. Reserved concurrency is not causing the issue.
- C
The table's read capacity is insufficient, causing write throttling
Why wrong: Incorrect. Read capacity is separate from write capacity. Write throttling is not caused by insufficient read capacity.
- D
The function is exceeding the DynamoDB item size limit of 400 KB
Why wrong: Incorrect. The items are approximately 1 KB, well below the 400 KB limit. Item size limits would cause errors but not ProvisionedThroughputExceededException.
Quick Answer
The answer is a single partition key causing hot partition throttling. This occurs because DynamoDB distributes its 500 WCUs across all partitions, but each partition has a hard limit of 1,000 WCU (or 3,000 with burst), so when all writes target the same key, that partition becomes a bottleneck even though the table’s total capacity is not fully used. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding that ProvisionedThroughputExceededException can arise from partition-level limits, not just table-level exhaustion—a common trap is assuming the 500 WCU table limit is the culprit. The key insight is that Lambda’s reserved concurrency and 10-item writes amplify the problem by flooding one partition. Remember: hot partitions happen when your workload lacks partition key diversity, so think “one key, one partition, one throttle.”
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 developer is troubleshooting an AWS Lambda function that writes items to an Amazon DynamoDB table. The function frequently fails with ProvisionedThroughputExceededException. The table has provisioned write capacity of 500 write capacity units (WCUs). The function has reserved concurrency of 10, and each invocation writes 10 items of approximately 1 KB each. There are no other writers to the table. What is the most likely cause of the 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 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
The function is writing to a single partition key, causing hot partition throttling
The most likely cause is that the function is writing to a single partition key, creating a 'hot partition' that exceeds the 1,000 WCU per-partition limit (or 3,000 WCU for burst capacity) even though the table's total provisioned capacity of 500 WCU is not exhausted. DynamoDB distributes throughput across partitions based on the partition key; if all writes target the same key, they are throttled at the partition level regardless of table-level 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 function is writing to a single partition key, causing hot partition throttling
Why this is correct
Correct. Hot partitions can cause throttling even when table-level capacity is sufficient. The function's writes are likely concentrated on one partition key, exceeding that partition's throughput limits.
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.
- ✗
The function's reserved concurrency is too high, causing excessive write requests
Why it's wrong here
Incorrect. With 10 WCUs per invocation and concurrency 10, maximum table usage is 100 WCUs, well below the provisioned 500 WCUs. Reserved concurrency is not causing the issue.
- ✗
The table's read capacity is insufficient, causing write throttling
Why it's wrong here
Incorrect. Read capacity is separate from write capacity. Write throttling is not caused by insufficient read capacity.
- ✗
The function is exceeding the DynamoDB item size limit of 400 KB
Why it's wrong here
Incorrect. The items are approximately 1 KB, well below the 400 KB limit. Item size limits would cause errors but not ProvisionedThroughputExceededException.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume table-level provisioned capacity is the only throttle boundary, but DynamoDB enforces per-partition throughput limits, so a hot partition can cause throttling even when the table's total WCU is not fully consumed.
Detailed technical explanation
How to think about this question
DynamoDB partitions data by partition key hash; each partition can handle up to 1,000 WCU (or 3,000 with burst) and 3,000 RCU. When all writes target the same partition key, they are serialized to that single partition, causing throttling even if the table's total provisioned capacity is underutilized. This is a common issue with sequential or monotonically increasing keys (e.g., timestamps), and can be mitigated by using write sharding or a more distributed partition key design.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The function is writing to a single partition key, causing hot partition throttling — The most likely cause is that the function is writing to a single partition key, creating a 'hot partition' that exceeds the 1,000 WCU per-partition limit (or 3,000 WCU for burst capacity) even though the table's total provisioned capacity of 500 WCU is not exhausted. DynamoDB distributes throughput across partitions based on the partition key; if all writes target the same key, they are throttled at the partition level regardless of table-level capacity.
What should I do if I get this DVA-C02 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
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Last reviewed: Jun 11, 2026
This DVA-C02 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 DVA-C02 exam.
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