PDE Storing the Data Practice Question
A global e-commerce platform requires a relational database that can handle millions of transactions per second across regions with strong consistency and automatic failover. The database must also support SQL joins. Which database should they choose?
⚠ Common exam trap
A common trap in the Google Professional Data Engineer exam is to assume Cloud SQL is suitable for global-scale, high-consistency workloads because it is a relational database, but it lacks the global distribution and automatic failover capabilities required for millions of transactions per second across 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 is the correct choice because it is a globally distributed, horizontally scalable relational database that provides strong consistency and automatic failover across regions, while fully supporting SQL joins. It combines the benefits of a traditional relational database with the horizontal scalability of NoSQL systems, making it ideal for high-throughput, globally distributed applications requiring ACID transactions.
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 Spanner
Why this is correct
Cloud Spanner satisfies the stem's demand for horizontal scalability with strong consistency by using TrueTime and Paxos across regions, delivering automatic failover and ANSI SQL joins. Unlike eventually consistent NoSQL stores, it preserves relational semantics at global scale, matching millions of transactions per second.
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Cloud SQL
Why it's wrong here
Cloud SQL is a single-region managed instance that cannot deliver cross-region strong consistency with automatic failover at millions of transactions per second. It is tempting because Cloud SQL is genuinely relational and supports SQL joins, and would be correct for a smaller regional application needing a conventional MySQL or PostgreSQL database.
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Cloud Firestore
Why it's wrong here
Cloud Firestore is a document NoSQL database; it offers no SQL join capability and its multi-region mode trades consistency for availability. It is tempting because Firestore scales globally with automatic replication, and would be correct for mobile or web app data needing flexible documents and real-time synchronisation rather than relational queries.
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Cloud Bigtable
Why it's wrong here
Cloud Bigtable is a wide-column NoSQL store without SQL joins, multi-row transactions or relational schema, so it cannot satisfy the joining requirement. It is tempting because Bigtable scales to millions of operations per second with strong consistency per row, and would be correct for high-throughput time-series or key-value analytics workloads.
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This PDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PDE exam.