The answer is the cluster’s maxmemory-policy is set to noeviction. This is the most likely cause because when an Amazon ElastiCache for Redis node reaches its allocated memory limit, the noeviction policy prevents any key eviction, causing writes to fail with the “OOM command not allowed when used memory > maxmemory” error. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of Redis memory management and eviction policies, often appearing as a trap where candidates confuse connection limits or cluster mode with memory constraints. A common mistake is to assume the error relates to sharding or keyspace notifications, but the error message explicitly points to memory exhaustion and a missing eviction strategy. Remember the mnemonic “No Eviction = No Room” to recall that without an eviction policy, writes are blocked once memory is full.
DBS-C01 Monitoring and Troubleshooting Practice Question
This DBS-C01 practice question tests your understanding of monitoring and troubleshooting. 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 application that writes to an Amazon ElastiCache for Redis cluster. The application occasionally fails with 'OOM command not allowed when used memory > maxmemory'. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The cluster's maxmemory-policy is set to noeviction.
Option C is correct because this error indicates the cache has reached its memory limit and eviction policy is not set or set to noeviction. Option A is wrong because that error is about keyspace notifications. Option B is wrong because cluster mode may affect sharding but not this specific error. Option D is wrong because connection limit would show a different error.
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 cluster's maxclients limit has been reached.
Why it's wrong here
Connection limit errors are different from OOM.
✓
The cluster's maxmemory-policy is set to noeviction.
Why this is correct
When memory is full and noeviction is set, writes fail with OOM.
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 cluster has too many keyspace notifications enabled.
Why it's wrong here
Keyspace notifications do not cause OOM errors.
✗
The cluster is in cluster mode and cross-slot commands are used.
Why it's wrong here
Cross-slot commands cause MOVED errors, not OOM.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
Cross-slot commands cause MOVED errors, not OOM.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 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
Got this wrong? Here's your next step.
Identify which DBS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Monitoring and Troubleshooting — This question tests Monitoring and Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The cluster's maxmemory-policy is set to noeviction. — Option C is correct because this error indicates the cache has reached its memory limit and eviction policy is not set or set to noeviction. Option A is wrong because that error is about keyspace notifications. Option B is wrong because cluster mode may affect sharding but not this specific error. Option D is wrong because connection limit would show a different error.
What should I do if I get this DBS-C01 question wrong?
Identify which DBS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
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Question Discussion
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