PCDE Manage a solution that can span multiple database technologies Practice Test 5 — 15 Questions

Question 1

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.)

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

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 2

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 3

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

Answer

Cloud Spanner

Answer

BigQuery

Question 4

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 5

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 volatile-lru policy evicts keys with an expire set (TTL) using the LRU algorithm. For a session store, sessions typically have a TTL, so volatile-lru is appropriate. allkeys-lru would evict any key regardless of TTL, which might remove important keys. noeviction would cause write errors when memory is full. volatile-ttl evicts based on TTL, not LRU.

Answer

allkeys-lru

Answer

noeviction

Answer

volatile-ttl

Question 6

A developer wants to add a composite index in Firestore to support a query that filters on two fields: 'status' (equality) and 'createdAt' (range). How should the index be configured?

Accepted Answer

Create a composite index with fields 'status' (ascending) and 'createdAt' (ascending).. Firestore requires a composite index when a query combines an equality filter on one field with a range filter on another. The index must list the equality field first ('status') followed by the range field ('createdAt'), with ascending order for both to support the range query efficiently. This matches the Firestore index definition rules for composite indexes.

Answer

No index is needed; single-field indexes are automatically created.

Answer

Create a composite index with fields 'createdAt' (ascending) and 'status' (ascending).

Answer

Add an index exemption on the 'status' field to force index creation.

Question 7

You are using Cloud Spanner and need to add a new column to an existing table. The table has millions of rows and must remain fully available for reads and writes during the schema change. What is the correct approach?

Accepted Answer

Use gcloud spanner databases ddl update with the ALTER TABLE statement; Spanner applies the change online.. Cloud Spanner supports non-blocking schema changes using DDL statements like ALTER TABLE ... ADD COLUMN. These operations are applied online without locking the table. The --async flag is optional for running the command asynchronously. The statement is executed via gcloud spanner databases ddl update.

Answer

Export the table using Dataflow, add the column locally, then import the data back.

Answer

Use gcloud spanner instances update to modify the table schema.

Answer

Take the instance offline, run the ALTER TABLE, then bring it back online.

Question 8

You notice that your Cloud SQL for MySQL instance's storage is filling up quickly. You have enabled automatic storage increase, but you want to manually increase the storage size by 50 GB to avoid any risk of reaching the limit. The current disk size is 200 GB. What is the correct gcloud command to resize the disk?

Accepted Answer

gcloud sql instances patch my-instance --storage-size 250. The `gcloud sql instances patch` command is used to modify an existing Cloud SQL instance, and the `--storage-size` flag expects the value in GB as an integer (without the 'GB' suffix). Specifying `250` correctly increases the storage from 200 GB to 250 GB.

Answer

gcloud sql instances patch my-instance --storage-size 250GB

Answer

gcloud sql instances update my-instance --storage-size 250

Answer

gcloud sql instances resize my-instance 250

Question 9

You need to monitor the disk usage of your Cloud SQL instances and receive an alert when disk usage exceeds 80%. Which GCP service should you use to set up this alert?

Accepted Answer

Cloud Monitoring. Cloud Monitoring (formerly Stackdriver) is the GCP service for monitoring metrics and setting up alerting policies. Cloud Logging is for logs, Cloud Audit Logs for audit trails, and Cloud Billing reports for cost tracking.

Answer

Cloud Audit Logs

Answer

Cloud Logging

Answer

Cloud Billing reports

Question 10

You have a Cloud Bigtable instance with a single cluster. To improve availability and durability, you want to enable replication across two regions. After configuring replication, you notice that reads from the replica cluster show data that is not yet consistent with the primary. What is the expected consistency model for Bigtable replication?

Accepted Answer

Eventually consistent reads from replicas. Cloud Bigtable replication uses an eventually consistent model for reads from replica clusters. When you write to the primary cluster, the data is asynchronously replicated to the replica cluster using a distributed replication pipeline. This means that reads from the replica cluster may return stale data until the replication process completes, and there is no guarantee of immediate consistency with the primary.

Answer

Read-your-writes consistency from the primary

Answer

Strongly consistent reads from any cluster

Answer

Strict serializability across clusters

Question 11

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.

Answer

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

Answer

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

Question 12

You are troubleshooting a Cloud SQL read replica that is experiencing high replication lag. You check the 'replication_lag' metric and see it is consistently above 60 seconds. What is the most likely cause of this lag?

Accepted Answer

The primary instance has a heavy write workload.. High replication lag in Cloud SQL is most commonly caused by a heavy write workload on the primary instance. When the primary processes a large volume of write operations (e.g., INSERT, UPDATE, DELETE), the replica must replay those changes from the binary log, and if the rate of writes exceeds the replica's ability to apply them, lag accumulates. This is a fundamental behavior of MySQL asynchronous replication, where the replica is always slightly behind the primary under load.

Answer

The replica's automatic storage increase is disabled.

Answer

The replica has point-in-time recovery enabled.

Answer

The replica is using a different storage type than the primary.

Question 13

Your Cloud Bigtable instance is experiencing hot spots, causing performance degradation. You want to identify the specific row keys causing the hot spots. Which tool should you use?

Accepted Answer

Key Visualiser. Key Visualiser is a Cloud Bigtable tool that visualises read/write traffic across the row key space, helping identify hot spots (rows with disproportionate traffic). Cloud Monitoring provides overall metrics but not row-level detail. Cloud Logging logs queries but not aggregated heat maps. cbt is the command-line tool for administrative tasks but does not provide visualisation.

Answer

Cloud Monitoring dashboard

Answer

cbt command-line tool

Answer

Cloud Logging

Question 14

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.. For point-in-time recovery within 7 days, Cloud Spanner offers built-in PITR (Option D) which enables restoring to any point within the retention period with minimal performance impact. Additionally, creating full backups (Option C) with a 7-day retention ensures you have backup files for restore if needed. Automating these backups with Cloud Scheduler (Option E) ensures regular backups without manual intervention. Options A and B are incorrect: A uses Dataflow export which is intended for long-term retention and can impact performance, and B restores from backups rather than enabling PITR. Option B is not needed when PITR is enabled.

Answer

Export the database daily using Dataflow to Cloud Storage.

Answer

Use gcloud spanner databases import to restore from previous exports.

Question 15

You are managing a Memorystore for Redis instance that is part of a high-traffic e-commerce application. The instance uses the volatile-lru eviction policy and has persistence disabled. You need to improve data durability without losing the ability to evict keys with TTL. You also want to ensure that the instance can automatically recover from a zonal failure. Which TWO actions should you take? (Choose TWO.)

Accepted Answer

Enable RDB persistence by setting the persistence mode.. (Enable RDB persistence) improves data durability by taking periodic snapshots without interfering with the volatile-lru eviction policy, which only evicts keys with TTL. Option D (Standard Tier with replication) provides automatic failover across zones within a region, ensuring recovery from a zonal failure. Option A only reduces eviction frequency but does not address durability or zonal failover. Option C is incorrect because Memorystore does not support native cross-region replicas. Option E uses manual exports, which do not enable automatic recovery and are not equivalent to persistence.

Answer

Increase the maxmemory setting to reduce eviction frequency.

Answer

Configure a cross-region replica to provide failover in another region.

Answer

Set up a Cloud Scheduler job to export the instance to Cloud Storage every hour.