PCDE Manage a solution that can span multiple database technologies Practice Test 8 — 15 Questions

Question 1

A Cloud SQL for MySQL instance is running low on disk space. You need to increase the storage without downtime. What is the correct approach?

Accepted Answer

Use the gcloud command to resize the storage; the operation is performed online.. Cloud SQL for MySQL supports online storage resizing using the `gcloud sql instances patch` command or the Google Cloud Console, which allows you to increase the storage capacity without any downtime. The operation is performed while the instance remains available, and the underlying persistent disk is resized live, leveraging Google Cloud's live resize capability for Cloud SQL instances.

Answer

Create a new instance with larger storage and migrate the data using mysqldump.

Answer

Enable automatic storage increase; resize manually is not possible.

Answer

Stop the instance, resize the attached persistent disk, then restart.

Question 2

You are running a Memorystore for Redis instance with persistence disabled. The application requires high availability and data durability after a zone failure. What is the most cost-effective approach?

Accepted Answer

Use a Standard tier instance with cross-zone replication.. Standard tier Memorystore for Redis instances provide cross-zone replication by default, ensuring automatic failover and data durability in the event of a zone failure. This meets the high availability and data durability requirements without the need for manual exports or complex multi-region setups, making it the most cost-effective solution.

Answer

Use a Basic tier instance and schedule periodic exports to Cloud Storage.

Answer

Enable persistence using the AOF or RDB configuration in Memorystore.

Answer

Deploy a Redis Cluster across multiple regions using Memorystore.

Question 3

A company uses Cloud Bigtable to store session data. They need to monitor replication lag between clusters in different zones. Which metric should they use?

Accepted Answer

Instance-level 'replication_lag' metric.. Cloud Bigtable exposes an instance-level 'replication_lag' metric that measures the time delay (in seconds) between clusters in a replicated instance. This metric directly reflects how far behind a replica cluster is relative to the primary cluster, making it the appropriate choice for monitoring replication lag between zones.

Answer

Cluster-level 'cpu_load' metric.

Answer

Use Key Visualizer to identify replication delays.

Answer

Table-level 'rows_returned' metric.

Question 4

A company has a Cloud SQL for PostgreSQL instance with a read replica in another region. They want to perform disaster recovery testing without affecting the primary. What should they do?

Accepted Answer

Promote the read replica to a standalone instance and use it for testing.. Promoting the read replica to a standalone instance detaches it from the primary, creating an independent writable Cloud SQL instance. This allows you to perform disaster recovery testing (e.g., failover validation, data integrity checks) without any impact on the primary instance, as the replica no longer replicates changes from the primary.

Answer

Use the replica as a failover target; testing is not allowed.

Answer

Enable point-in-time recovery on the replica and restore to a new instance.

Answer

Create a clone of the primary instance and test on that.

Question 5

A gaming company uses Cloud Spanner for a global leaderboard. They need to add a column to an existing table and create a secondary index on that column. The database must remain fully available during these changes. Which THREE statements are true?

Accepted Answer

The new column must have a default value if it is defined as NOT NULL.. In Cloud Spanner, when adding a NOT NULL column to an existing table, the column must have a DEFAULT value. This ensures that existing rows, which will be populated with the default value, satisfy the NOT NULL constraint without requiring a full table scan or blocking writes.

Answer

The new column cannot be added if the table has existing data.

Answer

CREATE INDEX will block writes on the table until the index is built.

Question 6

A company runs Memorystore for Redis with a Standard tier instance. They want to scale to higher throughput and memory capacity beyond the current tier limits. Which TWO actions should they take?

Accepted Answer

Enable Redis Cluster to shard data across multiple nodes.. Redis Cluster shards data across multiple nodes, allowing horizontal scaling beyond the limits of a single Standard tier instance. This enables higher throughput and memory capacity by distributing the dataset across multiple primary nodes, each handling a subset of the keyspace.

Answer

Switch from HDD to SSD storage.

Answer

Add a cross-region replica to increase read capacity.

Answer

Increase the maxmemory setting beyond the tier limit.

Question 7

A database administrator needs to restore a Cloud SQL for PostgreSQL instance to a specific point in time within the last 3 hours. Which configurations must be enabled to perform a point-in-time recovery (PITR)?

Accepted Answer

Automated backups and WAL archiving with a retention period. PITR in Cloud SQL for PostgreSQL requires automated backups enabled and write-ahead log (WAL) archiving with a specified transaction log retention period (1-7 days). Binary logging is for MySQL, not PostgreSQL.

Answer

Automated backups and binary logging

Answer

On-demand backups and binary logging

Answer

Automated backups and cross-region replicas

Question 8

An organization runs a Cloud SQL for MySQL instance for its e-commerce platform. During a load test, they notice the CPU utilization consistently exceeds 80% and queries are slowing down. The instance is using 2 vCPUs. The team needs to improve performance with minimal downtime. What should they do?

Accepted Answer

Increase the number of vCPUs and memory via vertical scaling. Increasing vCPUs and memory vertically (scaling up) is the quickest way to improve CPU-bound performance with minimal downtime. Cloud SQL supports online vertical scaling. Read replicas are for read offloading, not CPU-bound write performance. Auto-storage increase addresses storage, not CPU.

Answer

Create a cross-region read replica

Answer

Enable automatic storage increase

Answer

Shard the database using application-level sharding

Question 9

A financial services company uses Cloud Bigtable for real-time fraud detection. They have a cluster with 10 nodes using HDD storage and are experiencing high latency due to disk throughput bottlenecks. They need to improve performance with minimal downtime. What should they do?

Accepted Answer

Create a new cluster with SSD storage, replicate data, then update the application to point to the new cluster. Cloud Bigtable does not support in-place conversion of storage from HDD to SSD. The only way to migrate to SSD storage is to create a new cluster with SSD, replicate data using Bigtable replication, and then update the application connection string to point to the new cluster. This approach minimizes downtime by allowing the old cluster to serve reads during replication.

Answer

Modify the existing cluster's storage type to SSD via the Cloud Console

Answer

Use Cloud Bigtable's hot tablet detection to rebalance the data

Answer

Increase the number of nodes in the existing cluster

Question 10

A startup uses Memorystore for Redis as a session store. They are concerned about losing session data if the instance fails. Which option provides the best durability for session data without significant application changes?

Accepted Answer

Configure a cross-region replica to provide high availability. Configuring a cross-region replica in Memorystore for Redis provides high availability and durability by replicating data asynchronously to a replica instance in a different region. If the primary instance fails, the replica can be promoted, minimizing session data loss without requiring significant application changes, as the application continues to connect to the same endpoint or a new primary endpoint.

Answer

Increase the maxmemory setting to store more data

Answer

Take regular snapshots of the instance using gcloud commands

Answer

Enable Redis persistence (RDB/AOF) on the Memorystore instance

Question 11

A Cloud Spanner instance is backing up a 2 TB database daily to Cloud Storage using the built-in backup feature. The compliance team requires the backup to be stored in a specific regional bucket with a retention policy of 14 days. How should the database administrator configure this?

Accepted Answer

Use the gcloud spanner databases export command to export the database to a Cloud Storage bucket in the desired region, then set a retention policy on the bucket. Spanner database backups are stored as managed backups within the Spanner service, not directly as files in Cloud Storage. However, they can be exported to Cloud Storage using the export API. The export can be configured to a specific bucket and region, and object lifecycle rules can enforce retention.

Answer

Schedule a cron job to copy the backup from Spanner's default location to the regional bucket

Answer

Use the CREATE BACKUP statement and specify a Cloud Storage bucket in the desired region

Answer

Use the backup retention period in Spanner's backup settings to keep backups for 14 days

Question 12

A gaming company uses Firestore in Native mode to store player profiles and game state. They need to query the data by both 'playerId' and 'lastLoginTimestamp' sorted descending. The current index configuration is automatic. How should they configure indexing to support this query efficiently?

Accepted Answer

Create a composite index on 'playerId' ascending and 'lastLoginTimestamp' descending. Firestore automatically creates single-field indexes for all fields. For queries with ordering on two fields, a composite index is required. The composite index must include both fields in the correct order (ascending or descending).

Answer

Create two separate single-field indexes: one on 'playerId' and one on 'lastLoginTimestamp'

Answer

Use an exemption to remove automatic indexing on 'playerId' and rely on single-field indexes

Answer

Use the automatic index configuration; Firestore will create the necessary composite index automatically

Question 13

A DevOps engineer needs to monitor Cloud SQL for MySQL replication lag on a read replica to ensure data freshness. Which Cloud Monitoring metric should they create an alert on?

Accepted Answer

cloudsql.googleapis.com/database/replication/lag. The metric 'replication_lag' in Cloud SQL measures the seconds behind the primary. Cloud SQL for MySQL uses 'seconds_behind_master' internally, but the exposed metric is 'replication_lag'.

Answer

cloudsql.googleapis.com/database/replica/state

Answer

cloudsql.googleapis.com/database/postgresql/replication/lag

Answer

cloudsql.googleapis.com/database/mysql/replication/seconds_behind_master

Question 14

A company runs a Cloud SQL for PostgreSQL instance that is nearing its storage limit of 500 GB. The database administrator needs to increase storage capacity online without any downtime. What should they do?

Accepted Answer

Use the gcloud sql instances patch command with --storage-size flag. The `gcloud sql instances patch` command with the `--storage-size` flag allows you to increase the storage capacity of a Cloud SQL for PostgreSQL instance online without any downtime. Cloud SQL supports live storage increases by automatically resizing the underlying persistent disk while the instance remains available, so no restart or maintenance window is required.

Answer

Enable automatic storage increase and wait for it to trigger

Answer

Delete and recreate the instance with a larger disk

Answer

Shut down the instance, increase the disk size, and restart

Question 15

A large enterprise uses Cloud Bigtable for analytics. They notice that some nodes are handling significantly more traffic than others, causing hot spots and performance degradation. Which tool should they use to identify the specific row keys causing the issue?

Accepted Answer

Bigtable Key Visualiser. Key Visualiser is a Bigtable tool that provides a heatmap of row key access patterns, helping to identify hot spots by showing which row key ranges are heavily accessed.

Answer

Stackdriver Error Reporting

Answer

Bigtable cbt tool with read rows command

Answer

Cloud Monitoring dashboard for Bigtable