- A
Cloud Firestore in Datastore mode
Why wrong: Cloud Firestore in Datastore mode is a NoSQL document database that offers strong consistency and scalability, but its read latency is typically in the single-digit milliseconds, not microseconds.
- B
Cloud Bigtable
Why wrong: Cloud Bigtable is a scalable NoSQL database with high throughput, but its read latency is in the single-digit milliseconds, not microseconds. It does not meet the microsecond requirement.
- C
Cloud SQL (PostgreSQL)
Why wrong: Cloud SQL (PostgreSQL) is a relational database with typical read latency in milliseconds, not microseconds. It also has limited horizontal scalability.
- D
Cloud Memorystore (Redis)
Cloud Memorystore (Redis) provides microsecond read latency as an in-memory data store, supports horizontal scaling via sharding, and can be configured with persistence to ensure data survives for at least 30 days without activity.
Low-Latency Persistent Storage for Shopping Cart Data with Cloud Bigtable
This ACE practice question tests your understanding of microsecond latency. 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. A key principle to apply: microsecond latency. 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 are designing a solution for a retail application that needs to store customer shopping cart data. The cart data is accessed frequently during active sessions and must survive for at least 30 days even without activity. Each cart entry is small (< 1 KB) and identified by a user ID. The solution must support microsecond read latency and be horizontally scalable. Which GCP storage service best meets these requirements?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"least"Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Quick Answer
The answer is Cloud Bigtable. This service is the correct choice because it provides low-latency persistent storage for shopping cart data, offering consistent sub-10ms reads that can approach microsecond latency for small key-value lookups under 1 KB, while its fully managed, horizontally scalable architecture handles high-frequency access during active sessions and retains data indefinitely beyond the required 30 days. On the Google Associate Cloud Engineer exam, this scenario tests your ability to distinguish Bigtable from Cloud SQL or Firestore; a common trap is choosing Firestore for its real-time features, but Bigtable’s superior read latency and throughput for operational workloads make it the fit here. Remember the memory tip: “Bigtable for big speed and small keys” — when you need microsecond reads on tiny entries with no expiration, Bigtable is the persistent, scalable answer.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Cloud Memorystore (Redis)
Cloud Memorystore (Redis) is correct because it provides microsecond read latency as an in-memory data store, meeting the strict latency requirement. It can be configured with persistence (AOF or RDB) to ensure data survives at least 30 days without activity, and it supports horizontal scaling via sharding. Although often used as a cache, Cloud Memorystore with persistence satisfies all requirements for small, frequently accessed key-value entries like shopping cart data.
Key principle: Microsecond latency
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cloud Firestore in Datastore mode
Why it's wrong here
Cloud Firestore in Datastore mode is a NoSQL document database that offers strong consistency and scalability, but its read latency is typically in the single-digit milliseconds, not microseconds.
- ✗
Cloud Bigtable
Why it's wrong here
Cloud Bigtable is a scalable NoSQL database with high throughput, but its read latency is in the single-digit milliseconds, not microseconds. It does not meet the microsecond requirement.
- ✗
Cloud SQL (PostgreSQL)
Why it's wrong here
Cloud SQL (PostgreSQL) is a relational database with typical read latency in milliseconds, not microseconds. It also has limited horizontal scalability.
- ✓
Cloud Memorystore (Redis)
Why this is correct
Cloud Memorystore (Redis) provides microsecond read latency as an in-memory data store, supports horizontal scaling via sharding, and can be configured with persistence to ensure data survives for at least 30 days without activity.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Microsecond latency
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is that candidates may choose Cloud Bigtable for its high throughput and durability, but Bigtable offers only single-digit millisecond latency, not the required microsecond latency. Cloud Memorystore (Redis), with proper persistence configuration, provides both the low latency and durability needed.
Detailed technical explanation
How to think about this question
Bigtable uses a distributed, sorted key-value store built on Google's Colossus file system and SSTables, enabling automatic sharding and compaction for consistent low-latency access. Under the hood, it leverages Bigtable's tablet server architecture to distribute load across nodes, and row keys are lexicographically sorted to optimize range scans; for cart data, using a user ID as the row key ensures fast point lookups. A real-world scenario is an e-commerce platform handling millions of concurrent sessions where cart data must persist for abandoned carts; Bigtable's lack of automatic TTL (unless explicitly set with garbage collection) ensures data survives indefinitely, meeting the 30-day requirement without extra configuration.
KKey Concepts to Remember
- Microsecond latency
- Horizontal scalability
- Data persistence
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
Microsecond latency
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.
Review microsecond latency, then practise related ACE questions on the same topic to reinforce the concept.
Related practice questions
Related ACE practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Configuring Access and Security practice questions
Practise ACE questions linked to Configuring Access and Security.
Planning and Configuring a Cloud Solution practice questions
Practise ACE questions linked to Planning and Configuring a Cloud Solution.
Ensuring Successful Operation of a Cloud Solution practice questions
Practise ACE questions linked to Ensuring Successful Operation of a Cloud Solution.
Deploying and Implementing a Cloud Solution practice questions
Practise ACE questions linked to Deploying and Implementing a Cloud Solution.
Setting Up a Cloud Solution Environment practice questions
Practise ACE questions linked to Setting Up a Cloud Solution Environment.
ACE fundamentals practice questions
Practise ACE questions linked to ACE fundamentals.
ACE scenario practice questions
Practise ACE questions linked to ACE scenario.
ACE troubleshooting practice questions
Practise ACE questions linked to ACE troubleshooting.
Practice this exam
Start a free ACE practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this ACE question test?
Microsecond latency
What is the correct answer to this question?
The correct answer is: Cloud Memorystore (Redis) — Cloud Memorystore (Redis) is correct because it provides microsecond read latency as an in-memory data store, meeting the strict latency requirement. It can be configured with persistence (AOF or RDB) to ensure data survives at least 30 days without activity, and it supports horizontal scaling via sharding. Although often used as a cache, Cloud Memorystore with persistence satisfies all requirements for small, frequently accessed key-value entries like shopping cart data.
What should I do if I get this ACE question wrong?
Review microsecond latency, then practise related ACE questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Microsecond latency
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More ACE practice questions
- A team's Cloud Build pipeline must: (1) run unit tests, (2) build a Docker image only if tests pass, (3) push the image…
- A team needs a database backup job to run every day at 2 AM UTC. The job calls an HTTP endpoint to trigger the backup. T…
- A team wants to receive an email alert when the average CPU utilization of VMs in a managed instance group exceeds 80% f…
- A Go service is consuming significantly more CPU than expected. The team suspects an inefficient function but doesn't kn…
- A network team is creating a new VPC and must decide between auto mode and custom mode. Why would they choose custom mod…
- A company organizes its GCP projects by business unit — Finance, Engineering, and Sales. Which resource is best suited t…
Last reviewed: Jun 11, 2026
This ACE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ACE exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.