Google PCA Practice Question: Designing and Planning a Cloud Solution Architecture
This PCA practice question tests your understanding of designing and planning a cloud solution architecture. 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 moving a legacy application to Google Cloud. The application uses a PostgreSQL database and must be re-platformed with minimal code changes. They require high availability across zones and automatic failover within the same region. Which TWO database services meet these requirements? (Choose 2.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
AlloyDB for PostgreSQL
Cloud SQL for PostgreSQL provides regional high availability with automatic failover across zones. AlloyDB is PostgreSQL-compatible, offers high availability with a primary and standby instance, and is optimized for performance. Cloud Spanner is globally distributed but requires more code changes. Bigtable is not PostgreSQL-compatible. Firestore is NoSQL.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 for PostgreSQL
Why this is correct
AlloyDB is PostgreSQL-compatible, provides high availability, and requires minimal code changes.
Related concept
Static NAT maps one inside address to one outside address.
✓
Cloud SQL for PostgreSQL
Why this is correct
Cloud SQL for PostgreSQL offers zonal HA with automatic failover, minimal code changes.
Related concept
Static NAT maps one inside address to one outside address.
✗
Firestore
Why it's wrong here
Firestore is a NoSQL document database, not PostgreSQL-compatible.
✗
Cloud Bigtable
Why it's wrong here
Bigtable is a NoSQL database, not compatible with PostgreSQL.
✗
Cloud Spanner
Why it's wrong here
Spanner is not PostgreSQL-compatible; would require significant code changes.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCA NAT questions on configuration and troubleshooting.
Designing and Planning a Cloud Solution Architecture — This question tests Designing and Planning a Cloud Solution Architecture — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: AlloyDB for PostgreSQL — Cloud SQL for PostgreSQL provides regional high availability with automatic failover across zones. AlloyDB is PostgreSQL-compatible, offers high availability with a primary and standby instance, and is optimized for performance. Cloud Spanner is globally distributed but requires more code changes. Bigtable is not PostgreSQL-compatible. Firestore is NoSQL.
What should I do if I get this PCA question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCA NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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