Google PCA Design and plan a cloud solution architecture Practice Question
A retail company runs a Black Friday promotion and expects a burst of read traffic against a product-catalog database. The application is read-heavy, tolerates slightly stale data, and the team wants to scale reads horizontally without changing application code. They are using Cloud SQL for MySQL. Which design should the architect recommend?
⚠ Common exam trap
The trap here is assuming the high-availability standby can serve reads, when it is a non-readable failover target only.
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
✓
Configure a Cloud SQL read replica in the same region and point read queries at its IP address
Read replicas are the native Cloud SQL for MySQL mechanism for horizontal read scaling with asynchronous replication. Because the application tolerates slightly stale data, the replication lag is acceptable, and no code changes are needed beyond pointing read connections at the replica. A high-availability standby is not readable, Firestore requires a rewrite, and vertical scaling does not scale reads horizontally.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Cloud SQL high availability by adding a standby instance and send read queries to the standby
Why it's wrong here
A Cloud SQL high-availability standby is a failover target, not a readable endpoint. It receives synchronous replication and is inaccessible for queries while the primary is healthy, so directing read traffic there is not possible and the design would not scale reads at all during the promotion.
- ✗
Increase the primary instance's vCPU count and memory to absorb the read burst
Why it's wrong here
Vertical scaling increases the primary's capacity but does not scale reads horizontally, and Cloud SQL instance resizing requires a restart that causes downtime during a peak sales event. It also creates a single ceiling that the next promotion may exceed, so it is not the design the architect should recommend.
- ✗
Migrate the catalog to Firestore in Native mode and let the client SDK cache reads
Why it's wrong here
Firestore is a NoSQL document database with a different data model, so migrating the MySQL catalog requires application rewrites, which the team explicitly wants to avoid. Firestore also has different query semantics and consistency guarantees, making it a poor fit for a lift-and-shift read-scaling requirement.
- ✓
Configure a Cloud SQL read replica in the same region and point read queries at its IP address
Why this is correct
Cloud SQL for MySQL supports read replicas that receive asynchronous replication from the primary. Pointing read-only traffic at the replica IP offloads the primary and scales reads horizontally. The application tolerates slight staleness, which matches asynchronous replication, and no schema or code changes are needed beyond routing read connections.
Go deeper
Related to this question
Learn chapter
Data Migration and Transfer Services
Key term
Cloud SQL
Cloud SQL is a fully managed relational database service that lets you set up, maintain, and scale SQL databases (like MySQL, PostgreSQL, and SQL Server) in the cloud without managing the underlying infrastructure.
Key term
Firestore
Firestore is a flexible, scalable, serverless NoSQL database from Google Cloud that automatically syncs data across applications in real time.
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Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
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