Quick Answer
The answer is writes concentrated on a single partition key value. This is correct because DynamoDB distributes throughput evenly across partitions, and when a hot partition key like OrderID receives a disproportionate share of writes, that single partition can hit its hard limit of 3,000 WCU (provisioned) or 1,000 WCU (on-demand), causing throttling even when the table’s overall write capacity appears underutilized. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of partition-level throttling versus table-level metrics—a common trap is assuming that unused capacity elsewhere means no throttling should occur. Remember that DynamoDB’s throughput is per-partition, not per-table, so a single hot key can bottleneck the entire write path. A useful memory tip: think of a highway with ten lanes—if all cars crowd into one lane, that lane jams while the others remain empty, exactly like a hot partition key starving your writes.
This DEA-C01 practice question tests your understanding of data store management. 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.
Refer to the exhibit. A data engineer is troubleshooting write throttling on the Orders table. The table has a composite primary key (OrderID as partition key, CustomerID as sort key). The engineer notices that writes are throttled even though the write capacity is not fully utilized. What is the most likely cause?
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.
The table is empty and has no items.
Why wrong: Empty table would not cause throttling.
A global secondary index (GSI) is consuming write capacity.
Why wrong: No GSI is defined in the exhibit.
The read capacity units are too low.
Why wrong: Read capacity does not affect writes.
Writes are concentrated on a single partition key value.
Hot partition causes throttling even if total capacity is not exceeded.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Writes are concentrated on a single partition key value.
D is correct because write throttling on an Amazon DynamoDB table occurs when requests exceed the provisioned throughput for a specific partition, even if the overall table write capacity is underutilized. With a composite primary key where OrderID is the partition key, writes concentrated on a single OrderID value (e.g., a hot key) will hit that partition's 3,000 WCU or 1,000 WCU (on-demand) limit, causing throttling while other partitions remain idle.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The table is empty and has no items.
Why it's wrong here
Empty table would not cause throttling.
A global secondary index (GSI) is consuming write capacity.
Why it's wrong here
No GSI is defined in the exhibit.
The read capacity units are too low.
Why it's wrong here
Read capacity does not affect writes.
Writes are concentrated on a single partition key value.
Why this is correct
Hot partition causes throttling even if total capacity is not exceeded.
Clue confirmation
The clue words "most likely", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
AWS often tests the misconception that overall table capacity utilization is the sole indicator of throttling, but the trap here is that throttling can occur at the partition level due to hot keys, even when the table's total write capacity is underutilized.
Detailed technical explanation
DynamoDB partitions data by partition key hash; each partition has a fixed capacity of 3,000 read capacity units (RCU) or 1,000 write capacity units (WCU) for strongly consistent reads, and 3,000 WCU for writes under provisioned mode. When a single partition key receives excessive writes, it exhausts that partition's WCU budget, triggering ProvisionedThroughputExceededException, even if the table's total consumed WCU is below the provisioned limit. In real-world scenarios, this often happens with time-series data or popular items (e.g., a viral product) where OrderID values are not uniformly distributed.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
The correct answer is: Writes are concentrated on a single partition key value. — D is correct because write throttling on an Amazon DynamoDB table occurs when requests exceed the provisioned throughput for a specific partition, even if the overall table write capacity is underutilized. With a composite primary key where OrderID is the partition key, writes concentrated on a single OrderID value (e.g., a hot key) will hit that partition's 3,000 WCU or 1,000 WCU (on-demand) limit, causing throttling while other partitions remain idle.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This DEA-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 DEA-C01 exam.
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