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Google ACE Practice Question: A financial trading platform must support…
A financial trading platform must support globally distributed, strongly consistent SQL transactions at thousands of writes per second, with no downtime for planned maintenance. Which GCP database service meets all these requirements?
⚠ Common exam trap
Many candidates confuse Cloud Spanner's global strong consistency with Cloud SQL's regional strong consistency, or mistakenly think that NoSQL services like Bigtable or Firestore can support SQL transactions and global writes at scale.
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 only GCP database service that provides globally distributed, strongly consistent SQL transactions with horizontal scaling, supporting thousands of writes per second. It uses synchronous replication across regions and TrueTime-based clock synchronization to ensure external consistency, while also offering 99.999% availability with no planned downtime for maintenance.
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 SQL with synchronous read replicas
Why it's wrong here
Cloud SQL supports synchronous read replicas to offload read traffic, but write throughput remains limited to a single primary instance and can only scale vertically by increasing the machine size. For a financial trading platform, write-heavy workloads like incoming orders, trade executions, and balance updates would bottleneck on the primary's CPU, memory, and disk I/O; synchronous replicas also introduce network round-trip latency per write, and the architecture does not provide the horizontal write partitioning or global transaction ordering that Spanner offers.
- ✗
Cloud Bigtable
Why it's wrong here
Cloud Bigtable is a wide-column NoSQL database designed for high-throughput analytical and time-series workloads, but it does not support SQL queries or full ACID transactions. A financial trading platform requires relational integrity, multi-row atomicity, and consistency guarantees, none of which Bigtable provides; its write path is optimized for append-heavy analytics, not transactional order matching or trade settlement.
- ✗
Cloud Firestore
Why it's wrong here
Cloud Firestore is a document-oriented NoSQL database that offers strongly consistent reads and writes at the document level, but it lacks SQL query capability and does not provide across-document transaction semantics needed for integrated trading workflows. Its write throughput scales only with the number of documents and is constrained by the per-instance limits; moreover, it is built for mobile and web app data sync, not for the low-latency, high-consistency demands of a financial exchange.
- ✓
Cloud Spanner
Why this is correct
Cloud Spanner is the only Google Cloud database that natively combines SQL semantics, ACID transactions with external consistency (linearizable), and horizontal write scalability across regions, all backed by a 99.999% availability SLA. Its TrueTime API synchronizes globally distributed replicas so that transactions appear in a single, globally consistent order, which is exactly what a financial trading platform needs for order book updates, ledger entries, and risk management. This unique blend of relational structure, global consistency, and virtually unlimited write scaling makes Spanner the correct choice for mission-critical transactional systems.
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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.
Key term
Availability
Availability is the measure of how often a system or service is operational and accessible when needed, typically expressed as a percentage of uptime.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ACE 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 ACE exam.