PCDE Manage a solution that can span multiple database technologies Practice Test 2 — 15 Questions

Question 1

A Cloud Bigtable instance experiences a sudden increase in read latency and request errors. The operations team notices that one node is handling disproportionately more traffic. Which tool should they use to diagnose the issue?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Key Visualiser. Key Visualizer is the correct tool because it provides a heatmap of access patterns across row key ranges, allowing you to identify hot spots where a single node is overloaded due to uneven key distribution. This directly addresses the symptom of one node handling disproportionately more traffic, which is a common cause of increased latency and errors in Cloud Bigtable.

Answer

Stackdriver Monitoring dashboard

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gcloud bigtable instances describe

Answer

Use the cbt command to scan the table

Question 2

A company has a Cloud SQL for MySQL instance with automated backups enabled. They need to restore the database to a specific timestamp from 2 days ago. The backup retention is set to 7 days. How should they perform this restore?

Accepted Answer

Use gcloud sql instances clone with the --point-in-time flag and the desired timestamp. Cloud SQL for MySQL supports point-in-time recovery (PITR), which allows you to restore a database to a specific timestamp within the backup retention period (here, 7 days). The `gcloud sql instances clone` command with the `--point-in-time` flag creates a new instance that reflects the database state at the exact requested timestamp, leveraging the transaction logs retained by automated backups.

Answer

Export the database and import it into a new instance

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Create an on-demand backup and restore from that backup

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Use gcloud sql instances restore-backup with the backup ID from 2 days ago

Question 3

A Cloud SQL for MySQL instance is experiencing high CPU utilisation (>80%) and slow query performance. The instance has auto-storage increase enabled. Which step should the engineer take to immediately reduce CPU load?

Accepted Answer

Increase the instance tier to a larger machine type. Increasing the instance tier to a larger machine type immediately provides more CPU and memory resources, directly reducing CPU utilization and improving query performance. This is the most direct and immediate step to address high CPU on a Cloud SQL instance.

Answer

Reduce the max_connections parameter

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Create a cross-region read replica to offload reads

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Enable auto-storage increase if not already enabled

Question 4

A team is using Cloud SQL for PostgreSQL and wants to monitor replication lag on their read replicas. Which metric should they use?

Accepted Answer

cloudsql.googleapis.com/database/replication/lag. The metric cloudsql.googleapis.com/database/replication/lag is specifically designed to measure replication lag in Cloud SQL for PostgreSQL read replicas. It reports the time delay between the primary and replica, which is exactly what the team needs to monitor. Other metrics like network bytes, disk usage, or CPU utilization do not directly indicate replication lag.

Answer

cloudsql.googleapis.com/database/network/received_bytes_count

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cloudsql.googleapis.com/database/disk/bytes_used

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cloudsql.googleapis.com/database/cpu/utilization

Question 5

An organisation wants to back up their Cloud Spanner database and store the backup in a different region for disaster recovery. They require the backup to be in a format that can be restored into Spanner with minimal effort. Which THREE actions should they take? (Choose three.)

Accepted Answer

Specify a different location for the backup at creation time for cross-region storage. Cloud Spanner allows you to specify a different location for the backup at creation time, enabling cross-region storage for disaster recovery without additional export or import steps. Option D is correct because restoring a backup to a new database using `gcloud spanner databases restore` directly utilizes the backup format, requiring minimal effort. Option E is correct because creating a database-level backup using `gcloud spanner databases backup` is the native method to back up Spanner databases, and such backups can be stored in different regions for geographic redundancy.

Answer

Export the database using gcloud spanner databases export to CSV format

Answer

Use Dataflow to import the backup into a new instance

Question 6

A company is using Cloud SQL for PostgreSQL and needs to perform a disaster recovery drill by promoting a read replica to a standalone instance. They also need to ensure the replica is as current as possible before promotion. Which TWO steps should they take? (Choose two.)

Accepted Answer

Promote the replica using gcloud sql instances promote-replica. `gcloud sql instances promote-replica` is the standard command to promote a Cloud SQL read replica to a standalone instance, making it a primary that can accept writes. Option C is correct because checking the `replication_lag` metric ensures the replica has applied all pending changes from the primary before promotion, minimizing data loss. This step is critical because promoting a replica that is behind can result in lost transactions.

Answer

Enable binary logging on the replica

Answer

Create an on-demand backup of the primary before promotion

Answer

Force a failover to the replica

Question 7

A 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?

Accepted Answer

Cloud Bigtable. Cloud Bigtable is designed for exactly this use case — 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.

Answer

Firestore

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Cloud Spanner

Answer

BigQuery

Question 8

You are managing a Cloud SQL for PostgreSQL instance with point-in-time recovery (PITR) enabled. The retention period is set to 7 days. A developer accidentally dropped a critical table 3 days ago. You need to restore the database to the state just before the table was dropped, without affecting the current production instance. What should you do?

Accepted Answer

Use the gcloud sql instances clone command with the --point-in-time flag to clone the instance to a new instance at the timestamp just before the table was dropped.. The gcloud sql instances clone command with the --point-in-time flag allows you to create a new Cloud SQL instance that is a clone of the original at a specific timestamp. Since PITR is enabled and the retention period is 7 days, you can specify a timestamp just before the table was dropped (3 days ago) to restore the database to that exact state without affecting the current production instance. This approach meets the requirement of restoring to a point in time without overwriting the original instance.

Answer

Enable binary logging and reconfigure PITR retention to 10 days, then wait for the logs to catch up.

Answer

Use the gcloud sql backups create command to create an on-demand backup, then restore the original instance to that backup.

Answer

Use the gcloud sql instances restore-backup command to restore the original instance to the backup from 3 days ago.

Question 9

You have a Memorystore for Redis instance that serves as a session store for a web application. The instance is running low on memory and is approaching the maxmemory limit. You want to ensure that the least recently used keys are evicted first when memory is full. Which eviction policy should you configure?

Accepted Answer

volatile-lru. The requirement is to evict the least recently used keys when memory is full, but only among keys that have a TTL set. The volatile-lru policy evicts the least recently used keys among those with an expiration set, which matches the session-store use case where session keys carry TTLs. It preserves non-volatile keys (such as configuration or persistent data) from eviction, protecting critical data while reclaiming memory from expiring sessions.

Answer

allkeys-lru

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noeviction

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volatile-ttl

Question 10

You need to create a read replica of a Cloud SQL for PostgreSQL instance in a different region for disaster recovery. What must be true about the primary instance to support cross-region replicas?

Accepted Answer

The primary instance must have automated backups enabled.. Cross-region read replicas for Cloud SQL for PostgreSQL require automated backups to be enabled on the primary instance. Automated backups are necessary to maintain the WAL (Write-Ahead Log) archive, which is used for replication. The primary does not need to be regional; a zonal (non-HA) instance can also support cross-region replicas. Point-in-time recovery is automatically enabled when automated backups are on, and the flag 'cloudsql.logical_decoding' must be set to 'on' (not 'off') for PostgreSQL replication.

Answer

The primary instance must have point-in-time recovery disabled.

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The primary instance must be using a regional (high-availability) configuration.

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The primary instance must have the 'cloudsql.logical_decoding' flag set to 'off'.

Question 11

Your organisation uses Cloud Spanner for a globally distributed application. You need to set up a backup strategy that allows restoring the database to a specific point in time within the last 7 days, with minimal impact on performance. Which THREE actions should you take? (Choose THREE.)

Accepted Answer

Create full database backups using gcloud spanner backups create and set retention to 7 days.. Option C is correct because `gcloud spanner backups create` creates a full backup of the Spanner database, and setting the backup's `--retention-period` to 7 days (e.g., `7d`) satisfies the requirement to retain restore points for the last 7 days. Option D is correct because Cloud Spanner point-in-time recovery (PITR) lets you restore a database to any timestamp within a configurable retention window of up to 7 days, which directly enables restoring to a specific point in time within the last 7 days. Option E is correct because Cloud Scheduler can invoke `gcloud spanner backups create` on a recurring schedule, automating regular full backups with minimal operational overhead and no impact on query performance. Option A is not appropriate because exporting via Dataflow to Cloud Storage is a bulk export mechanism for data movement, not a native Spanner backup, and it does not provide point-in-time restore granularity. Option B is incorrect because `gcloud spanner databases import` is not the restore path for Spanner backups; restoring backups uses `gcloud spanner backups restore`, and imports from exports do not give point-in-time recovery.

Answer

Export the database daily using Dataflow to Cloud Storage.

Answer

Use gcloud spanner databases import to restore from previous exports.

Question 12

An organization needs to run a disaster recovery drill for its Cloud SQL for MySQL instance by promoting a read replica to a standalone instance. The replica is in the same region as the primary. After the drill, they want the original primary to resume serving writes. What should they do?

Accepted Answer

Promote the replica, then delete and recreate the replica from the original primary after the drill.. Promoting a read replica in Cloud SQL for MySQL breaks the replication link, making the replica a standalone primary. After the drill, you must delete the promoted replica and create a new read replica from the original primary to re-establish replication. This is the only supported method because Cloud SQL does not allow reversing the promotion or re-attaching a promoted instance as a replica.

Answer

Stop replication, then restart the primary instance to make it the new replica.

Answer

Use the gcloud command to switch roles between the primary and replica.

Answer

Promote the replica, then perform a failover on the original primary to make it the new primary.

Question 13

A Cloud Spanner database is experiencing high CPU utilization (above 80%). The team wants to add an index to optimize a frequently used query. The schema change must not cause downtime. How should they proceed?

Accepted Answer

Create the index using the Google Cloud Console; it will be applied online.. Spanner supports online schema changes; CREATE INDEX is non-blocking and can be executed via DDL without downtime.

Answer

Export the database, create the index in a new instance, then import.

Answer

Use gcloud spanner databases ddl update with --async flag.

Answer

Stop the application, run the DDL statement, then restart.

Question 14

An organization is using Cloud SQL for MySQL with automated backups enabled. They need to restore a backup to a new instance in a different region for testing. The backup is stored in the same region as the source. How can they achieve this with minimal operational overhead?

Accepted Answer

Restore the backup to a new instance in the same region, then use export/import to move data to the target region.. Cloud SQL backups are region-specific and cannot be restored directly to a different region. The minimal-operational-overhead approach is to restore the backup to a new instance in the same region, then use the export/import feature (e.g., SQL dump or CSV) to move the data to the target region. This avoids the complexity and cost of maintaining a cross-region read replica, while still achieving the goal with built-in tools.

Answer

Use gcloud sql backups restore with the --restore-instance flag pointing to a new instance in the target region.

Answer

Create a cross-region read replica from the source, then promote it in the target region.

Answer

Restore the backup directly to a new instance in the target region using the Cloud Console.

Question 15

A company uses Cloud Spanner and wants to export a database for long-term archival. The export must include the schema in a portable format. Which export option should they choose?

Accepted Answer

Create a database-level backup from the Cloud Console; it will export data and schema as Avro + Protobuf.. Spanner database backups are stored in Cloud Storage as Avro files with a Protobuf schema file, preserving both data and schema.

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Manually run SELECT statements to export data and DESCRIBE commands for schema.

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Use the Spanner migration tool to export to a SQL dump file.

Answer

Use gcloud spanner databases export with the --async flag to export to a Cloud Storage bucket in Avro format.