Google PCA Ensure solution and operations reliability Practice Question
An organization is migrating a legacy monolithic application to Google Cloud. The application currently runs on a single server with an on-premises database. The application is stateful and requires low-latency access to the database. The migration must minimize downtime and ensure high availability. Which architecture should the company adopt?
⚠ Common exam trap
The trap here is that candidates often overcomplicate the solution by choosing containerized or serverless options (GKE, Cloud Run, App Engine) without recognizing that a legacy monolithic stateful application with low-latency requirements is best served by a simple, proven VM-based architecture with regional persistent disks and a managed relational database with synchronous replication.
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
✓
Deploy on Compute Engine with a regional persistent disk and use Cloud SQL for PostgreSQL with regional high availability.
It combines Compute Engine with a regional persistent disk for synchronous replication across zones, ensuring high availability with minimal downtime during a zonal failure. Cloud SQL for PostgreSQL with regional high availability provides a managed, low-latency database with automatic failover, meeting the stateful application's need for low-latency access and high availability without the complexity of container orchestration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy on GKE with StatefulSets and use Cloud Spanner for global consistency.
Why it's wrong here
Cloud Spanner is a globally distributed, strongly consistent database whose multi-region replication adds write latency, contradicting the low-latency local database access the stateful monolith requires. It is tempting because Spanner suits globally distributed applications needing horizontal scale and consistency across continents, not a single-region lift-and-shift.
- ✓
Deploy on Compute Engine with a regional persistent disk and use Cloud SQL for PostgreSQL with regional high availability.
Why this is correct
A regional persistent disk keeps the stateful application's data synchronously replicated across zones, while Cloud SQL for PostgreSQL regional HA provides an automatic standby in a second zone. Together they deliver the required high availability and low-latency database access, and minimise downtime during cutover.
- ✗
Deploy on App Engine Standard Environment and use Cloud Firestore in Datastore mode.
Why it's wrong here
App Engine Standard runs stateless sandboxed instances with no persistent local disk, so a stateful monolith cannot retain session or file state there, and Firestore in Datastore mode is a NoSQL store, not a drop-in for the legacy relational database. It is tempting for stateless web apps needing automatic scaling.
- ✗
Deploy on Cloud Run and use Cloud SQL with read replicas.
Why it's wrong here
Cloud Run containers are ephemeral and stateless, so a stateful monolith loses in-memory session and local file state between requests, and Cloud SQL read replicas serve reads only, not the low-latency writes the application needs. It is tempting for stateless containerised APIs paired with a managed relational database.
Go deeper
Related to this question
Learn chapter
Google Cloud Resource Hierarchy and Organization
Key term
High availability
High availability is a system design approach that aims to keep applications and services operational and accessible with minimal downtime, even when some components fail.
Key term
Regional Persistent Disk
Regional Persistent Disk is a durable, block-level storage option in Google Cloud that automatically replicates data across two zones in a region to protect against zone failures.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.