20+ practice questions focused on Design for Reliability, Scalability, and Disaster Recovery — one of the most tested topics on the Google Professional Cloud DevOps Engineer exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Design for Reliability, Scalability, and Disaster Recovery PracticeA company needs to store petabytes of time-series IoT sensor data and query it with single-digit millisecond latency at millions of reads per second. The data has a simple key-value structure with timestamps. Which Google Cloud database is MOST appropriate?
Explanation: Cloud Bigtable is designed for petabyte-scale, low-latency (single-digit ms), high-throughput NoSQL storage for time-series, IoT, and financial data. It scales horizontally by adding nodes. BigQuery is optimised for analytics (seconds-to-minutes latency), Cloud SQL is for OLTP (limited to tens of thousands of QPS), and Firestore is for document data with hierarchical structure.
A company runs a Cloud SQL for PostgreSQL instance with a cross-region read replica in a different region for disaster recovery. The primary region experiences a complete outage. What is the expected RPO and RTO for promoting the read replica to become the new primary?
Explanation: Promoting a cross-region read replica involves manual intervention. The RPO equals the replication lag (which can be seconds to minutes depending on network and workload), not zero. The RTO is measured in minutes because you must verify the replica, promote it, and reconfigure applications. Cloud SQL HA failover (same region) achieves RPO near zero and RTO under 60 seconds, but cross-region replication is asynchronous.
A global financial services company requires a multi-region Spanner instance with an RPO of zero and an RTO of less than 5 seconds for a critical transactional workload. The application writes to a single region and reads from multiple regions. Which Spanner configuration should they choose?
Explanation: For zero RPO and sub-5-second RTO, a multi-region configuration with synchronous replication is needed. Spanner multi-region configurations like nam6 use synchronous replication across a primary and secondary region (with both read-write replicas). The leader region handles writes, and read-only replicas are for reads. A two-region multi-region config (e.g., nam6) provides synchronous replication (RPO=0) and automatic failover in <5 seconds. Three-region configs (nam-eur-asia1) have higher write latency due to longer distances.
A healthcare company uses Cloud Bigtable for patient event logs. They need to ensure data is available in another region in case of a regional outage. They set up a second cluster in a different region with replication. What is the RPO characteristic of Bigtable replication, and what routing policy ensures reads continue if the primary cluster fails?
Explanation: Bigtable replication is asynchronous, meaning the RPO is the replication lag (typically seconds to minutes). For automatic failover in reads, you can use the 'single-cluster routing' with a fallback or 'cluster-group routing' (any-replica) that sends requests to any available cluster. However, the question asks about routing policy to ensure reads continue if primary fails. The 'any-replica' routing policy sends read/write requests to the nearest available cluster, providing automatic failover. 'Read-failover' is not a standard term; there is a 'single-cluster routing' with 'allow writes from any cluster' but that's for writes.
A company uses AlloyDB for an e-commerce platform. They want to achieve the highest availability within a single region. What configuration should they use, and what is the expected failover RTO?
Explanation: AlloyDB offers an HA configuration with a primary instance and a standby (read pool) in different zones within the same region. Automatic failover occurs in less than 30 seconds. Cross-zone failover is automatic. There is no cross-region HA in AlloyDB (you can use cross-region replicas but that requires manual promotion).
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Practice all Design for Reliability, Scalability, and Disaster Recovery questions1. Baseline your knowledge
Start with 10 questions to gauge your current understanding of Design for Reliability, Scalability, and Disaster Recovery. This tells you whether you need a concept refresher or just practice.
2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Design for Reliability, Scalability, and Disaster Recovery questions on the PCDOE frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Design for Reliability, Scalability, and Disaster Recovery is tested as part of the Google Professional Cloud DevOps Engineer blueprint. Practicing with targeted Design for Reliability, Scalability, and Disaster Recovery questions ensures you can handle any format or difficulty that appears.
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