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Question 1,481 of 1,740

Monitoring and Logging →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the DynamoDB table is experiencing hot partitions due to uneven access patterns. This is correct because even with on-demand capacity mode, DynamoDB enforces a per-partition throughput limit of 3,000 read or 1,000 write request units per second; when a Lambda function writing from Kinesis Data Streams targets the same partition key repeatedly, that single partition can throttle HTTP 400 errors even though the table’s overall consumed write capacity remains well below the provisioned ceiling. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding that DynamoDB throttling is not always a capacity issue—it often stems from a hot partition key, a common trap where candidates blame Lambda concurrency or timeouts. A quick memory tip: think “hot key, cold table” to remember that a single partition can burn while the rest of the table stays idle.

DOP-C02 Monitoring and Logging Practice Question

This DOP-C02 practice question tests your understanding of monitoring and logging. 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 company uses AWS Lambda functions to process streaming data from Amazon Kinesis Data Streams. The Lambda function processes records in batches and writes the results to an Amazon DynamoDB table. Recently, the operations team noticed that the Lambda function is experiencing a high number of throttling errors (HTTP 400) when writing to DynamoDB. The DynamoDB table has on-demand capacity mode enabled. The CloudWatch metrics show that the DynamoDB consumed write capacity is well below the provisioned limits, but the Lambda function's error rate is increasing. The Lambda function's reserved concurrency is set to 100, and the function's timeout is 1 minute. The Kinesis stream has 10 shards. What is the MOST likely cause of the throttling errors?

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.

Question 1mediummultiple choice

Full question →

A
The DynamoDB table is experiencing hot partitions due to uneven access patterns.
On-demand capacity still has per-partition throughput limits; hot partitions can cause throttling.
B
The Lambda function's timeout is too short, causing the function to retry and overload DynamoDB.
Why wrong: Timeout does not cause DynamoDB throttling.
C
The Lambda function's reserved concurrency is too high, causing too many concurrent invocations.
Why wrong: High concurrency could cause throttling on the Kinesis side, but the error is from DynamoDB.
D
The Kinesis stream's batch size is too large, causing the Lambda function to write too many records at once.
Why wrong: Batch size affects the number of records per invocation, but DynamoDB throttling is per-partition, not per request size.

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

✓

The DynamoDB table is experiencing hot partitions due to uneven access patterns.

Option C is correct because the DynamoDB table has on-demand capacity, but throttling can still occur due to per-partition throughput limits. When many writes target the same partition key, the partition can throttle even if overall capacity is not exceeded. Option A is wrong because the function's concurrency is not the issue; throttling is from DynamoDB. Option B is wrong because the function timeout is not causing throttling. Option D is wrong because the batch size affects the number of records per invocation but not DynamoDB throttling directly.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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 DynamoDB table is experiencing hot partitions due to uneven access patterns.
Why this is correct
On-demand capacity still has per-partition throughput limits; hot partitions can cause throttling.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The Lambda function's timeout is too short, causing the function to retry and overload DynamoDB.
Why it's wrong here
Timeout does not cause DynamoDB throttling.
✗
The Lambda function's reserved concurrency is too high, causing too many concurrent invocations.
Why it's wrong here
High concurrency could cause throttling on the Kinesis side, but the error is from DynamoDB.
✗
The Kinesis stream's batch size is too large, causing the Lambda function to write too many records at once.
Why it's wrong here
Batch size affects the number of records per invocation, but DynamoDB throttling is per-partition, not per request size.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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.

Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.

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FAQ

Questions learners often ask

What does this DOP-C02 question test?

Monitoring and Logging — This question tests Monitoring and Logging — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: The DynamoDB table is experiencing hot partitions due to uneven access patterns. — Option C is correct because the DynamoDB table has on-demand capacity, but throttling can still occur due to per-partition throughput limits. When many writes target the same partition key, the partition can throttle even if overall capacity is not exceeded. Option A is wrong because the function's concurrency is not the issue; throttling is from DynamoDB. Option B is wrong because the function timeout is not causing throttling. Option D is wrong because the batch size affects the number of records per invocation but not DynamoDB throttling directly.

What should I do if I get this DOP-C02 question wrong?

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?

Static NAT maps one inside address to one outside address.

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