The answer is the Standard tier with AOF persistence enabled, because this combination provides both high availability through replication and durable data recovery via the Append-Only File. The Standard tier’s primary-replica architecture ensures automatic failover during node failures, while AOF persistence writes every write operation to a durable log on disk, allowing the session store to replay operations and restore state without loss. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of how Memorystore for Redis persistent configuration session store requirements differ between tiers—specifically, that the Basic tier lacks replication and cannot survive node failures, making it a common distractor. A frequent trap is assuming the Basic tier with AOF alone is sufficient, but without a replica, failover is impossible. Remember: for session durability, you need both a replica and a persistent log—think “Standard with AOF, not Basic with hope.”
PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. 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 database engineer is configuring a Memorystore for Redis instance for a session store application. The application requires persistent storage to survive node failures. Which tier and configuration should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Standard tier with AOF persistence enabled
The Standard tier in Memorystore for Redis provides a replicated architecture with a primary and read replica, ensuring high availability and automatic failover. Enabling AOF (Append-Only File) persistence writes every write operation to an AOF file, which is stored on persistent disk and can be replayed to restore data after a node failure. This combination meets the session store requirement for data durability across failures, as the Basic tier lacks replication and cannot guarantee data survival.
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.
✓
Standard tier with AOF persistence enabled
Why this is correct
Standard tier provides replication and failover; AOF persistence saves data to disk.
Related concept
Read the scenario before looking for a memorised answer.
✗
Standard tier with no persistence
Why it's wrong here
No persistence means data is lost on failover/restart.
✗
Basic tier with RDB persistence enabled
Why it's wrong here
Basic tier has no replica; failure leads to data loss even with persistence.
✗
Basic tier with AOF persistence enabled
Why it's wrong here
Basic tier has no replication, so node failure causes downtime and potential data loss.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that enabling persistence on any tier is sufficient, but the trap here is that the Basic tier lacks replication and automatic failover, so even with AOF persistence, a node failure causes downtime and potential data loss, which is unacceptable for a session store requiring high availability.
Detailed technical explanation
How to think about this question
AOF persistence in Redis works by logging every write operation to an append-only file, which can be replayed on restart to reconstruct the dataset. Memorystore for Redis uses a background process to rewrite the AOF file periodically to avoid unbounded growth, and the Standard tier ensures that the AOF file is replicated to the replica node. In a real-world session store, losing even a few seconds of session data can cause user logouts or corruption, making AOF with fsync every second a safer choice than RDB snapshots.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Standard tier with AOF persistence enabled — The Standard tier in Memorystore for Redis provides a replicated architecture with a primary and read replica, ensuring high availability and automatic failover. Enabling AOF (Append-Only File) persistence writes every write operation to an AOF file, which is stored on persistent disk and can be replayed to restore data after a node failure. This combination meets the session store requirement for data durability across failures, as the Basic tier lacks replication and cannot guarantee data survival.
What should I do if I get this PCDE 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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