Cloud Digital Leader Scaling with Google Cloud operations Practice Question
A startup is building a read-heavy mobile backend. They want a database that can scale out reads without downtime. Which database service should they choose?
⚠ Common exam trap
Google Cloud often tests the misconception that any NoSQL or globally distributed database is automatically better for scaling reads, when in fact Cloud SQL with read replicas is the simplest, most cost-effective, and downtime-free solution for a read-heavy relational workload.
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
✓
Cloud SQL with read replicas.
Cloud SQL with read replicas is the correct choice because it allows you to offload read traffic to one or more read replicas, scaling out reads without downtime. Read replicas are asynchronous replicas of the primary instance, and you can promote them to standalone instances if needed, making this ideal for a read-heavy mobile backend that requires high availability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cloud Firestore.
Why it's wrong here
Cloud Firestore is a NoSQL document database that automatically scales reads by distributing data and managing indexes, but it does not offer dedicated read replicas. This means you cannot provision explicit read-only instances to offload traffic or achieve predictable low-latency reads under heavy load, as scaling is handled internally and queries may face inconsistent performance. Additionally, Firestore's consistency model for multi-document queries is eventually consistent, which could be a drawback for a mobile backend requiring strong read-after-write guarantees.
- ✗
Cloud Spanner.
Why it's wrong here
Cloud Spanner, whilst offering excellent horizontal scalability for reads and writes, is primarily designed for globally distributed, strongly consistent transactional workloads. For a read-heavy mobile backend without an explicit requirement for global transactional integrity, its advanced capabilities and associated operational cost are typically excessive. It would be the correct choice for applications demanding strong consistency across multiple geographical regions, such as global financial systems or inventory management, where maintaining ACID properties across distributed transactions is critical.
- ✗
Cloud Bigtable.
Why it's wrong here
Cloud Bigtable is a wide-column NoSQL database optimized for large-scale analytical and operational workloads with high throughput, not for typical mobile backend patterns. It does not support SQL and is primarily accessed via the HBase API, making it a poor fit for a standard application stack. Furthermore, Bigtable only offers eventual consistency between replicated clusters, and its cluster management and pricing are designed for continuous high-volume data processing, making it overkill and operationally complex for a read-heavy mobile app that needs simple, consistent reads.
- ✓
Cloud SQL with read replicas.
Why this is correct
Cloud SQL with read replicas is the correct choice because Cloud SQL is a fully managed relational database (MySQL, PostgreSQL, or SQL Server) that provides strong consistency for reads and writes. Read replicas are asynchronous replicas of the primary instance that can serve read traffic, and this allows you to scale read capacity without downtime or architectural changes. Replicas can be promoted to primary if the original fails, and the SQL interface aligns naturally with most mobile backend APIs, making it a simple, cost-effective solution for a read-heavy workload.
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Cloud Digital Transformation
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
Service
A service is a software component or system that performs a specific function and is available to be used by other programs or users over a network.
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