A payments platform must keep one consistent ledger across three continents, scale writes horizontally, and still use SQL. Which product should the architect choose instead of Cloud SQL?
Show answer and explanation
Answer: C
Cloud Spanner is a relational database that speaks SQL, with strong consistency and horizontal scaling across nodes. Its multi-region configurations replicate data synchronously across regions while keeping transactions consistent. Cloud SQL runs standard engines such as MySQL, PostgreSQL and SQL Server on a single primary with read replicas, so write scaling depends on vertical growth and cross-continent consistency is not built in. Cloud Storage holds objects, not transactional rows.
Why the other options are wrong
- A. A bigger Cloud SQL instance adds only vertical capacity. Write throughput stays bound to one primary, and it does not provide synchronous consistency across continents.
- B. Cloud Storage holds objects and has no SQL query engine or multi-row transactions. A lifecycle policy only moves or deletes objects by age.
- D. Firestore is a document database, not a SQL database. Offline caching helps mobile clients but does not provide relational ledger semantics for this workload.