PCDOE Design for Reliability, Scalability, and Disaster Recovery Practice Test 3 — 15 Questions

Question 1

An organization requires a disaster recovery solution for Cloud SQL with a target RPO of less than 5 minutes and RTO of less than 2 hours. The primary region is us-central1, and the DR region is us-west1. Which approach should they use?

Accepted Answer

Create a cross-region read replica and promote it during disaster. Cross-region read replicas provide an RPO equal to replication lag (typically <5s) and RTO of minutes (manual promotion). This meets the requirements. Cross-region backup restore would have an RPO equal to the last backup age (hours) and RTO of hours. HA failover is for same-region only. PITR alone does not provide cross-region DR.

Answer

Use point-in-time recovery with daily backups and restore into a new instance

Answer

Configure a scheduled export of the database to Cloud Storage and import in DR region

Answer

Enable HA configuration in a single region

Question 2

A financial services company runs a global trading application on Cloud Spanner. They need the highest availability with 99.999% SLA and automatic failover with zero data loss. Which Spanner configuration should they choose?

Accepted Answer

Multi-region configuration nam-eur-asia1 (US, Europe, Asia). Multi-region configurations provide 99.999% SLA. Among the options, nam-eur-asia1 spans three continents with read-write replicas in each continent, offering automatic failover with zero data loss (RPO=0). Regional configuration offers 99.99% SLA. Multi-region with only read-only replicas in some regions does not achieve the same failover capability.

Answer

Regional configuration in us-central1 with read replicas

Answer

Multi-region configuration nam6 (US, limited to North America)

Answer

Regional configuration with a cross-region standby using backup/restore

Question 3

A media company uses Cloud Bigtable to serve user recommendations with low latency. They want to implement disaster recovery with a secondary cluster in a different region. They need automatic failover without manual DNS changes. Which routing policy should they configure?

Accepted Answer

Configure read-failover routing policy and use Cloud DNS health checks. The read-failover policy uses health checks to automatically route traffic to the secondary cluster if the primary becomes unhealthy. Any-replica sends requests to the closest cluster regardless of health. Manual DNS changes would be required for any-replica after a failure. Application-managed routing is not a built-in Bigtable feature.

Answer

Enable any-replica routing policy on the Bigtable cluster

Answer

Use single-cluster routing with manual DNS failover

Answer

Implement application-managed routing with a custom health check

Question 4

A company runs a critical e-commerce platform on Cloud SQL for PostgreSQL with cross-region read replicas for DR. During a recent disaster drill, they promoted the read replica to a standalone instance. After the drill, they attempted to re-create the replica but found that point-in-time recovery (PITR) was not enabled on the promoted instance. What is the most likely cause?

Accepted Answer

Automated backups and PITR are not enabled by default on the promoted instance. When a Cloud SQL read replica is promoted, it becomes a standalone primary instance. By default, automated backups and PITR are not enabled on the promoted instance. The original instance's configuration (including PITR) is not carried over. The user must manually enable these settings after promotion.

Answer

The backup retention policy on the original instance limited the PITR window

Answer

The cross-region replica connectivity was lost during promotion

Answer

The promoted instance does not support PITR because it was originally a read replica

Question 5

An organization needs to store backup copies of a Cloud Spanner database for a minimum of 365 days to comply with regulatory requirements. Which backup option should they use?

Accepted Answer

Create a Spanner backup and set the expiration to 365 days. Cloud Spanner backups can be configured with expiration up to 365 days (max). Import/export to Cloud Storage is not a managed backup solution and does not support PITR. Bigtable backups are for Bigtable, not Spanner. Cloud SQL backups are for Cloud SQL.

Answer

Enable point-in-time recovery (PITR) with a 365-day retention period

Answer

Export the database to Cloud Storage using the gcloud command and set a lifecycle policy

Answer

Use Cloud SQL for PostgreSQL with automated backups set to 365 days

Question 6

A DevOps engineer wants to test disaster recovery for a Cloud SQL for MySQL instance by simulating a zone failure without impacting production traffic. They need to ensure minimal data loss. Which approach should they take?

Accepted Answer

Promote a cross-region read replica in a test project to validate the failover process. Non-destructive tests are best done using read replicas. Promoting a read replica in a test environment avoids impacting production. Restoring a backup from Cloud Storage would not test the failover process. Using HA failover would affect production. Restoring to a new instance from PITR tests recovery but not failover.

Answer

Take an on-demand backup and restore it to a new Cloud SQL instance

Answer

Use the gcloud command to perform a point-in-time recovery on the same instance

Answer

Enable the HA configuration and trigger a failover by stopping the primary instance

Question 7

A company is designing a global user database that must support strong consistency and horizontal scaling with automatic failover. They have a 99.999% uptime requirement and need to serve writes from a single primary region with reads from multiple regions. Which Google Cloud database and configuration should they use?

Accepted Answer

Cloud Spanner multi-region configuration with a leader region and read-write and read-only replicas. Cloud Spanner multi-region with read-write replicas in one region (leader) and read-only replicas in others provides strong consistency, global reads, and automatic failover. Bigtable is eventually consistent. Cloud SQL cannot span multiple regions natively. Firestore does not provide 99.999% SLA.

Answer

Cloud Firestore in multi-region mode

Answer

Cloud Bigtable with replication and any-replica routing

Answer

Cloud SQL for PostgreSQL with cross-region read replicas and auto-failover

Question 8

A social media company uses Cloud Spanner with a multi-region configuration. During a regional outage, automatic failover occurred, but some transactions that were in-flight at the time of failure were lost. What is the most likely reason for this data loss?

Accepted Answer

The multi-region configuration included read-only replicas in some regions, causing loss of recent writes. In a multi-region Spanner configuration, the leader region handles writes. If a transaction was committed but not yet replicated to other regions before the leader region failed, it could be lost if the new leader region does not have that data. However, Spanner's multi-region configurations are designed for RPO=0 (no data loss) when using read-write replicas. If read-only replicas are used in some regions, data loss can occur because those replicas do not participate in the voting. The most common cause of data loss in Spanner multi-region is a misconfiguration where not all regions have read-write replicas.

Answer

The database had schema changes that were not replicated to standby replicas

Answer

The transaction isolation level was set to read committed instead of serializable

Answer

The application did not retry failed transactions after the failover

Question 9

A startup is building a mobile app and needs a fully managed database that scales automatically for unpredictable workloads. They expect moderate read/write traffic with occasional spikes. They want minimal operational overhead and do not need global distribution. Which Google Cloud database is MOST appropriate?

Accepted Answer

Cloud Firestore in native mode. Cloud Firestore is fully managed, serverless, auto-scales, and ideal for mobile apps with moderate traffic. Cloud SQL requires manual scaling. Bigtable is overkill and complex for this workload. Spanner is designed for global scale and is more complex than needed.

Answer

Cloud SQL for PostgreSQL with HA

Answer

Cloud Spanner regional

Answer

Cloud Bigtable

Question 10

A company uses AlloyDB for PostgreSQL for their operational database. They want to ensure automatic failover with the shortest possible RTO. Which configuration should they use?

Accepted Answer

Deploy a multi-zone AlloyDB cluster with automatic failover enabled. AlloyDB provides automatic failover with RTO under 60 seconds. Cross-zone failover in a multi-zone cluster provides the best availability within a region. Cross-region replication is not automatic and requires manual promotion. Basic instances offer no HA. Read pool failover is not automatic.

Answer

Deploy a single-zone AlloyDB cluster with a read pool

Answer

Configure a cross-region read replica and set up automated promotion scripts

Answer

Use an AlloyDB basic (single-node) instance

Question 11

A company uses Cloud Bigtable for their analytics pipeline. They set up replication with a primary cluster in us-central1 and a secondary in us-west1. They notice that during normal operation, queries always hit the primary cluster even if the secondary is closer. What should they change to route queries to the nearest cluster automatically?

Accepted Answer

Change the app profile routing policy to any-replica. The default routing policy for Bigtable replication is single-cluster (to the primary). To route to the nearest healthy cluster, they need to enable the any-replica routing policy in their Bigtable app profile. read-failover is for DR failover, not for normal operations. Changing the primary cluster does not solve the routing issue. Client-side logic is an option but not a built-in solution.

Answer

Implement client-side logic to choose which cluster to query

Answer

Modify the primary cluster to be in us-west1

Answer

Update the app profile to use read-failover routing

Question 12

An organization needs to define RTO and RPO for their database disaster recovery plan. They have a Cloud SQL for SQL Server instance with HA enabled. What are the typical RTO and RPO for an automatic HA failover?

Accepted Answer

RPO: near zero, RTO: under 60 seconds. Cloud SQL HA failover is automatic within the same region. It provides RPO near zero (minimal data loss) and RTO typically under 60 seconds.

Answer

RPO: replication lag (seconds), RTO: minutes

Answer

RPO: zero, RTO: zero

Answer

RPO: minutes, RTO: hours

Question 13

A company is using Cloud Spanner and wants to perform disaster recovery testing. They need to validate that their backup and restore process works without impacting production. Which TWO actions should they take? (Choose 2 correct answers.)

Accepted Answer

Restore a backup to a new database in the same instance using a different database ID. Restoring a backup to a new instance in a separate project is non-destructive and tests the restore process. Using a different database ID in the same instance also tests restore without overriding production. Option C is destructive (deletes production). Option D is not about testing. Option E is not a built-in feature for Spanner.

Answer

Export the database to Cloud Storage and import it into a new instance

Answer

Perform a failover to a read replica and then fail back

Answer

Directly restore a backup to the production database to test recovery time

Question 14

A company uses Cloud SQL for PostgreSQL with cross-region read replicas for DR. They want to automate the failover process to reduce RTO. Which THREE components should they include in their automation? (Choose 3 correct answers.)

Accepted Answer

A script to promote the cross-region read replica to a primary instance using gcloud sql instances promote-replica. To automate cross-region failover, you need to detect the primary failure (health check), promote the replica (gcloud command), and update DNS to point to the new primary. Option A is not needed because the replica is already set up. Option D is not required as the replica is already created. Option E would increase complexity unnecessarily.

Answer

A configuration to automatically create a new read replica after promotion

Answer

A script to create a new read replica in the DR region

Answer

A Cloud DNS managed zone with a weighted routing policy to split traffic evenly across regions

Question 15

A company is evaluating disaster recovery options for their production Bigtable instance. They need asynchronous replication with manual failover and the ability to route reads to the secondary cluster only when the primary is unhealthy. Which TWO settings should they configure? (Choose 2 correct answers.)

Accepted Answer

Use Cloud DNS health checks to update DNS records to point to the secondary cluster. Bigtable replication uses app profiles. To achieve manual failover with routing to secondary only when primary is unhealthy, they should configure a read-failover routing policy on an app profile. They should not use any-replica because that would route reads to the secondary during normal operation. Option A is automatic, not manual. Option D is not a valid routing policy. Option E would not meet the requirement of using secondary only when primary unhealthy.

Answer

Enable automatic failover by setting the replication to synchronous mode

Answer

Configure a multi-cluster routing policy with a single-cluster fallback

Answer

Create an app profile with any-replica routing policy