The answer is to set the reserved concurrency to a value greater than zero and to enable the event source mapping if it is disabled. A reserved concurrency of 0 acts as a hard throttle, meaning the Lambda function has zero execution slots available, so it cannot process any invocations, including those from an SQS queue. Even if the event source mapping is active, the service will fail to invoke the function because no capacity exists. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how reserved concurrency interacts with event source mappings—a common trap is assuming the queue or mapping is misconfigured when the real issue is a concurrency ceiling. Remember that setting reserved concurrency to 0 is effectively a kill switch for all invocations. A useful memory tip: "Zero concurrency means zero executions, so raise the floor to let the queue pour."
SOA-C02 Monitoring, Logging, and Remediation Practice Question
This SOA-C02 practice question tests your understanding of monitoring, logging, and remediation. 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 SysOps administrator is troubleshooting a Lambda function that is not processing messages from an SQS queue. The function is subscribed to the queue via an event source mapping. The function has a reserved concurrency of 0. Which TWO actions will resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the reserved concurrency to a value greater than 0.
Reserved concurrency of 0 means the Lambda function has no available execution capacity, so it cannot process any invocations, including those from SQS. Setting reserved concurrency to a value greater than 0 (e.g., 1 or more) allocates the necessary execution slots for the function to run. This directly resolves the issue because the event source mapping will successfully invoke the function only when concurrency is available.
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.
✗
Add SQS permissions to the Lambda execution role.
Why it's wrong here
Permissions are necessary but not the issue here; the function cannot execute due to concurrency.
✗
Configure a dead-letter queue for the Lambda function.
Why it's wrong here
A dead-letter queue handles failed messages but does not enable processing.
✓
Set the reserved concurrency to a value greater than 0.
Why this is correct
Reserved concurrency of 0 prevents any invocation; setting it to a positive value enables execution.
Related concept
Read the scenario before looking for a memorised answer.
✓
Enable the event source mapping if it is disabled.
Why this is correct
If the mapping is disabled, no messages are processed regardless of concurrency.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the batch size in the event source mapping.
Why it's wrong here
This would not help if the function cannot execute due to zero concurrency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often overlook reserved concurrency of 0 as a valid configuration that completely blocks invocations, and instead focus on permissions or queue settings, not realizing that a concurrency limit of 0 is a deliberate disablement mechanism.
Detailed technical explanation
How to think about this question
Reserved concurrency sets a hard limit on the number of concurrent executions for a function; a value of 0 effectively disables the function by preventing any new invocations. The event source mapping for SQS polls the queue and invokes the function synchronously, but if the function has no available concurrency, the invocation is throttled and messages remain in the queue. In real-world scenarios, setting reserved concurrency to 0 is sometimes used to temporarily disable a function without deleting the event source mapping, but it must be increased to allow processing.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Monitoring, Logging, and Remediation — This question tests Monitoring, Logging, and Remediation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set the reserved concurrency to a value greater than 0. — Reserved concurrency of 0 means the Lambda function has no available execution capacity, so it cannot process any invocations, including those from SQS. Setting reserved concurrency to a value greater than 0 (e.g., 1 or more) allocates the necessary execution slots for the function to run. This directly resolves the issue because the event source mapping will successfully invoke the function only when concurrency is available.
What should I do if I get this SOA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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