- A
BigQuery
Why wrong: BigQuery is for analytics, but the scenario does not specify analytics as a separate database; it could be used, but the question asks for two databases for the given purposes.
- B
Memorystore
For low-latency key-value session data.
- C
Firestore
Why wrong: Firestore is a document database, but Memorystore is better for session caching with lower latency.
- D
Cloud Spanner
Why wrong: Spanner is globally distributed relational, but not needed for a simple catalog; Cloud SQL is sufficient.
- E
Cloud SQL
For the relational product catalog.
Question 826 of 980
PCD Practice Question: Manage a Solution that Can Span Multiple Database Systems
This PCD practice question tests your understanding of manage a solution that can span multiple database systems. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 is designing a polyglot persistence architecture for an e-commerce platform. They need to store product catalog (relational), session data (low-latency key-value), and analytics data (large-scale SQL queries). Which TWO Google Cloud databases should they use? (Choose two.)
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
✓
Memorystore
Memorystore is correct because it provides a managed in-memory data store (Redis or Memcached) that delivers sub-millisecond latency for session data, which is a key-value workload requiring fast reads and writes. This directly satisfies the low-latency key-value requirement for session management in the polyglot persistence architecture.
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.
- ✗
BigQuery
Why it's wrong here
BigQuery is for analytics, but the scenario does not specify analytics as a separate database; it could be used, but the question asks for two databases for the given purposes.
- ✓
Memorystore
Why this is correct
For low-latency key-value session data.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Firestore
Why it's wrong here
Firestore is a document database, but Memorystore is better for session caching with lower latency.
- ✗
Cloud Spanner
Why it's wrong here
Spanner is globally distributed relational, but not needed for a simple catalog; Cloud SQL is sufficient.
- ✓
Cloud SQL
Why this is correct
For the relational product catalog.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between 'low-latency key-value' and 'relational' requirements, leading candidates to incorrectly choose Cloud Spanner for session data because it is a database, or Firestore because it is a key-value store, without recognizing that Memorystore is the only option purpose-built for in-memory, sub-millisecond key-value access.
Trap categories for this question
Scenario analysis trap
BigQuery is for analytics, but the scenario does not specify analytics as a separate database; it could be used, but the question asks for two databases for the given purposes.
Detailed technical explanation
How to think about this question
Memorystore uses the Redis protocol (RESP) or Memcached ASCII protocol, allowing direct use of existing client libraries and commands like GET/SET for session tokens. Under the hood, it stores all data in RAM with optional persistence to disk via AOF or RDB snapshots, but for session data, the ephemeral nature is acceptable, and the sub-millisecond latency is achieved by avoiding disk I/O. In a real-world e-commerce platform, session data is typically stored with a TTL (time-to-live) to auto-expire, which Memorystore supports natively via the EXPIRE command.
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
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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Manage a Solution that Can Span Multiple Database Systems — study guide chapter
Learn the concepts, then practise the questions
- →
Manage a Solution that Can Span Multiple Database Systems practice questions
Targeted practice on this topic area only
- →
All PCD questions
980 questions across all exam domains
- →
Google Professional Cloud Developer study guide
Full concept coverage aligned to exam objectives
- →
PCD practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related PCD practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Manage a Solution that Can Span Multiple Database Systems practice questions
Practise PCD questions linked to Manage a Solution that Can Span Multiple Database Systems.
Deploy Scalable and Highly Available Databases in Google Cloud practice questions
Practise PCD questions linked to Deploy Scalable and Highly Available Databases in Google Cloud.
Design Scalable and Highly Available Cloud Database Solutions practice questions
Practise PCD questions linked to Design Scalable and Highly Available Cloud Database Solutions.
Migrate Data Solutions practice questions
Practise PCD questions linked to Migrate Data Solutions.
Designing highly scalable, available, and reliable cloud-native applications practice questions
Practise PCD questions linked to Designing highly scalable, available, and reliable cloud-native applications.
Building and testing applications practice questions
Practise PCD questions linked to Building and testing applications.
Deploying applications practice questions
Practise PCD questions linked to Deploying applications.
Integrating Google Cloud services practice questions
Practise PCD questions linked to Integrating Google Cloud services.
Managing application performance monitoring practice questions
Practise PCD questions linked to Managing application performance monitoring.
PCD fundamentals practice questions
Practise PCD questions linked to PCD fundamentals.
PCD scenario practice questions
Practise PCD questions linked to PCD scenario.
PCD troubleshooting practice questions
Practise PCD questions linked to PCD troubleshooting.
Practice this exam
Start a free PCD 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 PCD question test?
Manage a Solution that Can Span Multiple Database Systems — This question tests Manage a Solution that Can Span Multiple Database Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Memorystore — Memorystore is correct because it provides a managed in-memory data store (Redis or Memcached) that delivers sub-millisecond latency for session data, which is a key-value workload requiring fast reads and writes. This directly satisfies the low-latency key-value requirement for session management in the polyglot persistence architecture.
What should I do if I get this PCD 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.
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 →
Last reviewed: Jul 4, 2026
This PCD 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 PCD 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.