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Google PCA Practice Question: Migrating an on-premises Oracle database to…
A company is migrating an on-premises Oracle database to Google Cloud. They want to minimize application changes and need a fully managed, PostgreSQL-compatible database with high performance for OLTP workloads. Which service is MOST suitable?
⚠ Common exam trap
PCA often tests the distinction between Cloud SQL (general-purpose, smaller workloads) and AlloyDB (high-performance OLTP), tricking candidates into choosing Cloud SQL simply because it is also PostgreSQL-compatible and fully managed.
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 for PostgreSQL is Google Cloud's fully managed, PostgreSQL-compatible database engine purpose-built for high-performance OLTP, offering up to 4x faster transactional throughput than standard PostgreSQL and a columnar engine for analytics. Because it is wire-compatible with PostgreSQL, applications using standard drivers and SQL need minimal changes, satisfying the migration goal. Its managed nature offloads backups, replication, and patching, which fits the 'fully managed' requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Bigtable
Why it's wrong here
Bigtable is a wide-column NoSQL store with no SQL dialect, schemas, or Oracle compatibility, so relational applications cannot run unchanged. It is tempting because it delivers very high throughput for massive time-series and analytical workloads, and would be correct for that access pattern rather than transactional OLTP.
- ✓
AlloyDB
Why this is correct
AlloyDB provides a fully managed, PostgreSQL-compatible engine with a columnar acceleration layer, delivering the high OLTP throughput the stem demands. Its compatibility allows the Oracle application to migrate with minimal code changes, satisfying both the performance and low-modification constraints simultaneously.
- ✗
Cloud SQL for PostgreSQL
Why it's wrong here
Cloud SQL for PostgreSQL caps storage and provides no Oracle syntax compatibility, so Oracle PL/SQL and proprietary features require application rewrites. It is tempting because it is fully managed and PostgreSQL-compatible, and would be correct for smaller OLTP workloads where Oracle-specific code has already been refactored.
- ✗
Cloud Spanner
Why it's wrong here
Cloud Spanner uses GoogleSQL or PostgreSQL-dialect interfaces but is not Oracle-compatible, so PL/SQL and Oracle-specific constructs demand application changes. It is tempting because it is fully managed and scales horizontally for high-performance OLTP, and would be correct for globally distributed workloads built without Oracle dependencies.
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Key term
AlloyDB
AlloyDB is a fully managed, PostgreSQL-compatible database service from Google Cloud designed for high performance, scalability, and reliability for transactional and analytical workloads.
Key term
OLTP
OLTP (Online Transaction Processing) is a data processing system designed to manage and record high volumes of real-time transactions, such as bank deposits or online purchases, quickly and reliably.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
This PCA 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 PCA exam.