This PCDE practice question tests your understanding of monitor and optimize database performance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 Cloud Memorystore for Redis instance used as a session store has a high eviction rate. Which configuration change can reduce evictions while maintaining performance?
Enable persistence (RDB)
Why wrong: Persistence does not affect evictions; it adds write overhead.
Increase number of replicas
Why wrong: Replicas do not reduce evictions on the primary instance.
Decrease timeout
Why wrong: Lower timeout may cause more frequent evictions of expired keys.
Set maxmemory-policy to allkeys-lru
This evicts least recently used keys, ideal for session data.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Set maxmemory-policy to allkeys-lru
Option D is correct because setting `maxmemory-policy` to `allkeys-lru` allows Redis to evict the least recently used keys across all keys when memory is full, which directly reduces eviction rates by ensuring that only the least active session data is removed. This maintains performance by keeping frequently accessed session keys in memory, which is critical for a session store where active sessions are repeatedly read and written.
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.
Enable persistence (RDB)
Why it's wrong here
Persistence does not affect evictions; it adds write overhead.
Increase number of replicas
Why it's wrong here
Replicas do not reduce evictions on the primary instance.
Decrease timeout
Why it's wrong here
Lower timeout may cause more frequent evictions of expired keys.
Set maxmemory-policy to allkeys-lru
Why this is correct
This evicts least recently used keys, ideal for session data.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Google Cloud often tests the misconception that increasing replicas or enabling persistence can solve memory pressure issues, when in fact only adjusting the eviction policy or increasing `maxmemory` directly addresses evictions.
Detailed technical explanation
Redis eviction occurs when the `maxmemory` limit is reached, and the `maxmemory-policy` determines which keys are removed. The `allkeys-lru` policy uses an approximation of the Least Recently Used algorithm (based on the `LRU` clock and a sample of keys) to evict keys that are least likely to be accessed again, which is ideal for session stores where session data has varying activity levels. In contrast, `volatile-lru` only evicts keys with an expiration set, which can lead to higher eviction rates if many session keys lack TTLs.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
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FAQ
Monitor and optimize database performance — This question tests Monitor and optimize database performance — Read the scenario before looking for a memorised answer..
The correct answer is: Set maxmemory-policy to allkeys-lru — Option D is correct because setting `maxmemory-policy` to `allkeys-lru` allows Redis to evict the least recently used keys across all keys when memory is full, which directly reduces eviction rates by ensuring that only the least active session data is removed. This maintains performance by keeping frequently accessed session keys in memory, which is critical for a session store where active sessions are repeatedly read and written.
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 30, 2026
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