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Design Scalable and Highly Available Cloud Database Solutions →easyMultiple ChoiceObjective-mapped

PCD Practice Question: Design Scalable and Highly Available Cloud Database Solutions

This PCD practice question tests your understanding of design scalable and highly available cloud database solutions. 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 wants to run hybrid transactional/analytical processing (HTAP) workloads on a PostgreSQL-compatible database with built-in columnar engine for faster analytical queries. Which Google Cloud database should they choose?

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

✓

AlloyDB

AlloyDB is a PostgreSQL-compatible database service with a built-in columnar engine that accelerates analytical queries by storing data in columns rather than rows, enabling HTAP workloads without needing to move data between separate transactional and analytical systems. Its architecture decouples compute from storage and uses a columnar cache to deliver up to 100x faster analytical queries than standard PostgreSQL, making it the correct choice for HTAP on Google Cloud.

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.

  • ✓

    AlloyDB

    Why this is correct

    AlloyDB is PostgreSQL-compatible and includes a columnar engine for fast analytics.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    Cloud SQL for PostgreSQL

    Why it's wrong here

    Cloud SQL for PostgreSQL does not have a columnar engine.

  • ✗

    Cloud Spanner

    Why it's wrong here

    Spanner is not PostgreSQL-compatible and lacks a columnar engine.

  • ✗

    BigQuery

    Why it's wrong here

    BigQuery is an analytics data warehouse, not suitable for OLTP or PostgreSQL compatibility.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse Cloud SQL for PostgreSQL as capable of HTAP because it supports read replicas and some analytical extensions, but it lacks a native columnar engine, so it cannot handle mixed workloads efficiently without performance degradation.

Detailed technical explanation

How to think about this question

AlloyDB's columnar engine works by automatically offloading analytical queries to a columnar cache that is populated from the row-based storage engine, using a technique called 'columnar projection' to avoid full table scans. Under the hood, it leverages a disaggregated storage architecture with a log-structured merge tree (LSM) for writes, while the columnar engine uses vectorized execution and predicate pushdown to achieve sub-second query times on terabytes of data. In a real-world scenario, an e-commerce platform can run real-time inventory analytics and order processing on the same AlloyDB instance, eliminating the latency and complexity of ETL pipelines between separate OLTP and OLAP systems.

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.

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FAQ

Questions learners often ask

What does this PCD question test?

Design Scalable and Highly Available Cloud Database Solutions — This question tests Design Scalable and Highly Available Cloud Database Solutions — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: AlloyDB — AlloyDB is a PostgreSQL-compatible database service with a built-in columnar engine that accelerates analytical queries by storing data in columns rather than rows, enabling HTAP workloads without needing to move data between separate transactional and analytical systems. Its architecture decouples compute from storage and uses a columnar cache to deliver up to 100x faster analytical queries than standard PostgreSQL, making it the correct choice for HTAP on Google Cloud.

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.

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Last reviewed: Jul 4, 2026

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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.