The answer is that the cache is under memory pressure and evicting keys to make room, which is the most likely cause of a sudden ElastiCache cache hit ratio drop. When an ElastiCache Redis cluster runs out of allocated memory, it begins evicting keys based on its configured eviction policy—such as allkeys-lru—to free space for new writes. This eviction removes cached session data that would have otherwise served future requests, forcing the application to fall back to the backend database and causing the hit ratio to plummet. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how memory management directly impacts caching effectiveness, often appearing as a trap where candidates mistakenly blame network issues or configuration changes. A key memory tip: if you see a sustained hit ratio drop without a full outage, think "eviction, not disruption"—the cache is still online, but it’s silently discarding valuable data to stay within its memory limit.
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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's production environment uses an Amazon ElastiCache Redis cluster for session caching. The operations team reports that the cache hit ratio has dropped significantly, causing increased load on the backend database. 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 cache is under memory pressure and evicting keys to make room.
Option B is correct because a dropped cache hit ratio often indicates that cached keys are being evicted due to memory pressure, especially if the eviction policy is set to 'allkeys-lru' or similar. Option A is wrong because a cluster mode change would cause a temporary disruption but not necessarily a sustained drop in hit ratio. Option C is wrong because a network partition would cause complete cache unavailability, not just a drop in hit ratio. Option D is wrong because encryption in transit does not affect cache performance.
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 cache is under memory pressure and evicting keys to make room.
Why this is correct
When memory is full, eviction removes keys, reducing hit ratio.
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 was resized from a single node to a cluster mode.
Why it's wrong here
Resizing might cause a brief flush but not a sustained drop.
✗
The encryption in transit was enabled, adding latency.
Why it's wrong here
Encryption adds latency but does not cause key eviction.
✗
There is a network partition between the application and the cache.
Why it's wrong here
A partition would cause cache misses entirely, not a drop in hit ratio.
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.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which DOP-C02 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.
Incident and Event Response — This question tests Incident and Event Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The cache is under memory pressure and evicting keys to make room. — Option B is correct because a dropped cache hit ratio often indicates that cached keys are being evicted due to memory pressure, especially if the eviction policy is set to 'allkeys-lru' or similar. Option A is wrong because a cluster mode change would cause a temporary disruption but not necessarily a sustained drop in hit ratio. Option C is wrong because a network partition would cause complete cache unavailability, not just a drop in hit ratio. Option D is wrong because encryption in transit does not affect cache performance.
What should I do if I get this DOP-C02 question wrong?
Identify which DOP-C02 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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