Quick Answer
The answer is the IteratorAge metric. This is correct because IteratorAge measures the age in milliseconds of the last record in the Lambda function’s iterator, directly reflecting how far behind real-time processing has fallen. When records fail processing, Lambda retries them, causing the iterator to stall and the age to spike or trend upward, making IteratorAge the ideal indicator of processing failures rather than a simple count of failed records. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this question tests your understanding of Kinesis-Lambda integration monitoring, often appearing as a trap where candidates mistakenly choose `MillisBehindLatest` (which measures consumer lag, not per-record retry failures). A key memory tip: think of IteratorAge as the “stuck record” metric—when processing fails, the iterator ages like milk left out, spoiling your throughput.
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 is using AWS Lambda to process streaming data from Amazon Kinesis. The processing rate is slower than expected, and the engineer needs to monitor the number of records that are failing processing. Which metric should be used to create a CloudWatch alarm?
Invocations
Why wrong: Invocations counts total invocations, not failures.
IteratorAge
IteratorAge measures the age of the last record processed; high values indicate backlog.
Errors
Why wrong: Errors count function errors, but not necessarily processing failures from Kinesis.
Throttles
Why wrong: Throttles indicate throttled invocations, not processing failures.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
IteratorAge
The IteratorAge metric measures the age of the last record in the Lambda function's iterator, indicating how far behind real-time the processing is. A high or increasing IteratorAge suggests that records are being retried or stuck due to processing failures, making it the correct metric to monitor for records failing processing in a Kinesis-triggered Lambda.
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.
Invocations
Why it's wrong here
Invocations counts total invocations, not failures.
IteratorAge
Why this is correct
IteratorAge measures the age of the last record processed; high values indicate backlog.
Related concept
Read the scenario before looking for a memorised answer.
Errors
Why it's wrong here
Errors count function errors, but not necessarily processing failures from Kinesis.
Throttles
Why it's wrong here
Throttles indicate throttled invocations, not processing failures.
Common exam traps
The trap here is that candidates confuse 'Errors' (Lambda function exceptions) with 'record processing failures' in a Kinesis stream, not realizing that Kinesis retries failed batches internally, so the Lambda may not emit an error metric for each failed record.
Detailed technical explanation
Under the hood, when a Lambda function fails to process a batch from Kinesis, the stream's iterator does not advance, causing the IteratorAge to increase as new records pile up. The Lambda function can also use a DLQ (Dead Letter Queue) for failed records, but IteratorAge is the native CloudWatch metric that directly reflects processing lag, which is a proxy for record failures. In real-world scenarios, a sudden spike in IteratorAge often precedes a downstream system failure, making it a proactive alarm trigger.
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
Monitoring and Logging — This question tests Monitoring and Logging — Read the scenario before looking for a memorised answer..
The correct answer is: IteratorAge — The IteratorAge metric measures the age of the last record in the Lambda function's iterator, indicating how far behind real-time the processing is. A high or increasing IteratorAge suggests that records are being retried or stuck due to processing failures, making it the correct metric to monitor for records failing processing in a Kinesis-triggered Lambda.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This DOP-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 DOP-C02 exam.
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