Question 690 of 1,446
Design innovative, scalable, and highly available cloud database solutions →mediumMultiple SelectObjective-mapped
PCDE Strong global consistency Practice Question
A company is evaluating Google Cloud databases for a new application that requires: (1) strong global consistency across multiple regions, (2) the ability to run complex analytical queries on the same data as the transactional workload, and (3) high write throughput. Which TWO databases should they consider?
⚠ Common exam trap
Candidates often assume AlloyDB provides strong global consistency because of its marketing around 'global scale' and 'cross-region replication', but in reality its cross-region replication is eventually consistent. Cloud Spanner is the only Google Cloud database offering strong global consistency across multiple regions.
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 Spanner
Cloud Spanner provides strong global consistency across multiple regions via multi-region configurations using synchronous replication, high write throughput (up to 20,000 writes per second per node, scalable), and support for transactional workloads. However, it does not natively handle complex analytical queries on the same data; for HTAP, a separate analytics engine like BigQuery or a dedicated HTAP database such as AlloyDB would be needed. AlloyDB offers HTAP and high write throughput, but its cross-region replication is eventually consistent, failing the strong global consistency requirement. BigQuery lacks transactional strong consistency and high write throughput. Bigtable provides eventual consistency and no SQL analytical queries. Firestore offers strong consistency only within a single region and no complex analytical queries. Thus, only Cloud Spanner fully meets the three requirements.
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 provides eventual consistency, not strong global consistency, and does not support complex analytical queries in SQL. It is optimized for real-time analytics on time-series data, not transactional workloads.
- ✗
AlloyDB
Why it's wrong here
AlloyDB offers high write throughput and HTAP (columnar engine for analytics), but its cross-region replication using AlloyDB Omni is eventually consistent, failing the strong global consistency requirement.
- ✗
BigQuery
Why it's wrong here
BigQuery is a data warehouse for analytical queries, not a transactional database. It cannot provide strong global consistency for writes or high write throughput for OLTP workloads.
- ✗
Firestore
Why it's wrong here
Firestore provides strong consistency only within a single region; multi-region is eventually consistent. It does not support complex analytical queries and has lower write throughput for transactional applications.
- ✓
Cloud Spanner
Why this is correct
Cloud Spanner meets all three: strong global consistency via synchronous multi-region replication, high write throughput (scalable), and support for transactional workloads. It does not natively run complex analytical queries, but that can be addressed with external analytics tools.
Visual reference
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Same concept, more angles
8 more ways this is tested on PCDE
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a database solution for a global social media application that requires strong consistency, high write throughput, and complex relational queries. Which TWO Google Cloud databases should they consider? (Choose 2)
medium- A.Cloud Bigtable
- B.BigQuery
- ✓ C.Cloud Spanner
- D.Firestore
- ✓ E.AlloyDB for PostgreSQL
Why C: Cloud Spanner provides global strong consistency and relational support. AlloyDB offers strong consistency and high performance for relational workloads. Bigtable is eventually consistent. BigQuery is analytical. Firestore is not globally consistent.
Variation 2. An organization needs a fully managed, globally distributed relational database with strong consistency and horizontal scaling for a multi-region application. Which service meets these requirements?
easy- A.Bigtable
- B.Firestore
- C.Cloud SQL
- ✓ D.Cloud Spanner
Why D: Cloud Spanner provides global distribution, strong consistency, horizontal scaling, and relational features.
Variation 3. A financial services company is migrating a legacy on-premises OLTP application to Google Cloud. The application requires high transaction rates (thousands per second), strict ACID compliance, and the ability to scale horizontally across multiple regions with strong consistency. Which Google Cloud database service should the company choose?
easy- A.Bigtable
- B.Cloud SQL for PostgreSQL
- C.Firestore
- ✓ D.Cloud Spanner
Why D: Cloud Spanner is a globally distributed, horizontally scalable relational database service that provides ACID transactions and strong consistency across regions. It is ideal for OLTP workloads that require high throughput, consistency, and global scalability.
Variation 4. A startup needs a database for its new web application that will serve a global user base. The application requires low-latency reads and writes (single-digit milliseconds), strong consistency, and the ability to handle high concurrency (thousands of transactions per second). Which Google Cloud database service should the startup choose?
easy- A.Cloud SQL for MySQL
- ✓ B.Cloud Spanner
- C.Bigtable
- D.Firestore
Why B: Cloud Spanner offers global distribution, strong consistency, and low-latency transactions at high concurrency. It is designed for globally scaled OLTP workloads.
Variation 5. A company needs to choose a Google Cloud database for a globally distributed application that requires strong consistency across continents and an SLA of 99.999% for availability. Which database service meets these requirements?
easy- A.Cloud Bigtable
- B.Cloud SQL
- C.Firestore
- ✓ D.Cloud Spanner
Why D: Cloud Spanner is the only Google Cloud database that provides global strong consistency and a 99.999% availability SLA when using a multi-region configuration. Bigtable offers only eventual consistency across regions, Cloud SQL is regional, and Firestore provides strong consistency only within a single region.
Variation 6. A company is building a microservices architecture and needs to choose a database per service. Which THREE factors should they consider?
easy- ✓ A.Consistency requirements
- B.Preferred programming language
- ✓ C.Expected query patterns
- ✓ D.Data size and growth rate
- E.Number of developers
Why A: Consistency requirements are critical because different databases offer varying consistency models (e.g., ACID vs. BASE). For example, a financial transaction service requiring strong consistency would need a relational database like PostgreSQL, while a social media feed could tolerate eventual consistency with a NoSQL database like Cassandra. Choosing based on consistency ensures data integrity aligns with business needs.
Variation 7. A startup needs a database for a global user base with low-latency reads and writes, strong consistency, and the ability to scale horizontally without downtime. They anticipate variable traffic. Which Google Cloud database service meets these requirements?
easy- A.Cloud Bigtable
- B.Cloud SQL
- C.Firestore
- ✓ D.Cloud Spanner
Why D: Cloud Spanner provides global distribution, strong consistency, horizontal scaling, and no downtime for schema changes or scaling. Cloud SQL is not global, Bigtable does not have strong consistency, and Firestore is not global with strong consistency for multi-region.
Variation 8. A company needs a fully managed, relational database with strong consistency and global distribution for a travel booking application that supports high concurrency and ACID transactions. Which Google Cloud database should they choose?
easy- A.Cloud SQL
- ✓ B.Cloud Spanner
- C.Cloud Bigtable
- D.Firestore
Why B: Cloud Spanner is the correct choice because it is a fully managed, globally distributed relational database that provides strong consistency and ACID transactions across regions, making it ideal for high-concurrency travel booking applications that require global distribution and transactional integrity.
Last reviewed: Jul 4, 2026
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