Quick Answer
The answer is to increase the instance size or set a TTL policy on session keys. This is correct because a high eviction rate in Memorystore for Redis signals that the instance has reached its `maxmemory` limit, forcing Redis to evict keys based on the configured `maxmemory-policy`; by either scaling up the instance to provide more memory or enforcing TTLs on session keys, you directly reduce memory pressure and prevent unnecessary evictions of active data. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of Redis memory management under the Memorystore service, and a common trap is to immediately tweak the eviction policy instead of addressing the root cause—insufficient memory or unmanaged key expiration. Remember the mnemonic “Size or TTL, evictions will settle” to recall that the first step is always to either allocate more memory or ensure keys expire gracefully.
This PCDE practice question tests your understanding of monitor and optimize database performance. 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.
You have a Memorystore for Redis instance used as a session store. You notice that the instance is experiencing high eviction rates. What is the best first step to take?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Increase the instance size or set a TTL policy on session keys.
More memory or key expiration reduces evictions.
Monitor memory usage but take no action.
Why wrong: Inaction will lead to data loss.
Add a read replica to offload read traffic.
Why wrong: Read replicas do not reduce memory usage on the primary.
Enable persistence (AOF or RDB) to reduce memory usage.
Why wrong: Persistence consumes additional memory, not reduces it.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Increase the instance size or set a TTL policy on session keys.
High eviction rates in Memorystore for Redis indicate that the instance is running out of memory and the Redis `maxmemory-policy` is actively removing keys. The best first step is to either increase the instance size to provide more memory or set a TTL (Time-To-Live) policy on session keys so that expired sessions are cleaned up proactively, reducing memory pressure and evictions.
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.
Increase the instance size or set a TTL policy on session keys.
Why this is correct
More memory or key expiration reduces evictions.
Clue confirmation
The clue words "best", "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Monitor memory usage but take no action.
Why it's wrong here
Inaction will lead to data loss.
Add a read replica to offload read traffic.
Why it's wrong here
Read replicas do not reduce memory usage on the primary.
Enable persistence (AOF or RDB) to reduce memory usage.
Why it's wrong here
Persistence consumes additional memory, not reduces it.
Common exam traps
Google Cloud often tests the misconception that persistence (AOF/RDB) frees memory, but persistence only affects durability, not memory usage, and candidates may confuse read replicas as a solution for memory pressure rather than read throughput.
Detailed technical explanation
Redis eviction occurs when the `used_memory` exceeds `maxmemory`, and the configured `maxmemory-policy` (e.g., `allkeys-lru`, `volatile-ttl`) determines which keys are removed. For session stores, setting a TTL on keys allows Redis to proactively expire data via its lazy and active expiration mechanisms, reducing the need for eviction. In Memorystore, the `maxmemory` is tied to the instance tier (e.g., 1 GB for M1), so scaling up to a higher tier is the direct way to increase capacity.
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
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: Increase the instance size or set a TTL policy on session keys. — High eviction rates in Memorystore for Redis indicate that the instance is running out of memory and the Redis `maxmemory-policy` is actively removing keys. The best first step is to either increase the instance size to provide more memory or set a TTL (Time-To-Live) policy on session keys so that expired sessions are cleaned up proactively, reducing memory pressure and evictions.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best", "first". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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