PCDE Manage a solution that can span multiple database technologies Practice Test 9 — 15 Questions

Question 1

You have a Cloud Spanner database that needs to be migrated from one region to another. You want to ensure no data loss and minimal downtime. Which approach should you use?

Accepted Answer

Create a backup of the database and restore it to a new instance in the target region.. Cloud Spanner does not support in-place region changes or read replicas in different regions. The only supported method to migrate a Cloud Spanner database between regions with no data loss and minimal downtime is to create a backup of the database and restore it to a new instance in the target region. This approach ensures a consistent snapshot of the data and allows you to plan the cutover window to minimize downtime.

Answer

Use gcloud spanner instances move to change the region of the existing instance.

Answer

Create a read replica in the target region and promote it after replication catches up.

Answer

Use gcloud command 'gcloud spanner databases export' to export the database to CSV files, then import into the new instance.

Question 2

Your Cloud Bigtable instance uses HDD storage. You need to change to SSD to improve read performance. What is the correct procedure?

Accepted Answer

Create a new cluster with SSD storage in the same instance, replicate data, then delete the old cluster.. Cloud Bigtable does not support changing the storage type of an existing cluster in place. The supported migration path is to add a new cluster with SSD storage to the same instance, allow Bigtable's built-in replication to sync the data, then delete the old HDD cluster. This preserves data and avoids downtime because the instance continues serving reads/writes throughout the replication and cutover.

Answer

Use Cloud Bigtable's online storage migration feature to switch to SSD without downtime.

Answer

Update the instance's storage type using 'gcloud bigtable instances update' with the --storage-type flag.

Answer

Export the HDD cluster's data to Cloud Storage, then import into a new SSD cluster.

Question 3

You need to monitor the replication lag between a Cloud SQL for MySQL primary instance and its read replica. Which metric should you use to set up an alert?

Accepted Answer

cloudsql.googleapis.com/database/replication/replication_lag. Cloud SQL exposes a metric 'replication/replication_lag' (or 'cloudsql.googleapis.com/database/replication/replication_lag') that measures the lag in seconds between the primary and replica. This is the correct metric for alerting.

Answer

cloudsql.googleapis.com/database/replication/replica_count

Answer

cloudsql.googleapis.com/database/cpu/utilization

Answer

cloudsql.googleapis.com/database/memory/utilization

Question 4

Your Firestore database in Native mode contains a collection with millions of documents. You need to query documents where the 'tags' field (an array) contains the string 'urgent'. What must you ensure in your index configuration?

Accepted Answer

No additional index configuration is required; Firestore automatically creates the necessary index for array fields.. Firestore automatically creates a single-field index for array fields. However, to query array-contains, you need an index on the field with the array-contains filter. Firestore automatically creates a single-field index for the 'tags' field, so no additional index is needed. If the query includes additional equality clauses, a composite index may be required, but for a simple array-contains, it's automatic.

Answer

Ensure the 'tags' field is not indexed, and then create a composite index with the array-contains filter.

Answer

Create an index exemption for the 'tags' field to enable array queries.

Answer

Create a composite index on 'tags' and '__name__' for the collection.

Question 5

Your company runs a global e-commerce platform on Cloud Spanner. You need to capture real-time changes to a table (e.g., orders) and stream them to a downstream analytics pipeline in near real-time. Which TWO Google Cloud features or services should you combine to achieve this? (Choose two.)

Accepted Answer

Dataflow streaming pipeline. A Dataflow streaming pipeline can consume Cloud Spanner change streams in near real-time, process the data (e.g., transform, filter, aggregate), and write it to a downstream analytics system. Dataflow provides exactly-once processing semantics and auto-scaling, making it ideal for continuous change data capture (CDC) pipelines.

Answer

Cloud Functions

Answer

Cloud Pub/Sub

Answer

Cloud SQL for PostgreSQL

Question 6

You are designing a disaster recovery plan for a Cloud Bigtable instance. The instance has a single cluster in us-east1. You need to ensure that if the cluster becomes unavailable, the database can still serve read and write requests with minimal downtime. Which THREE steps should you take? (Choose three.)

Accepted Answer

Ensure the application can handle eventual consistency between clusters.. Cloud Bigtable uses eventual consistency for replication across clusters. When you add a second cluster and enable replication, data is replicated asynchronously, so writes to one cluster are not immediately visible in the other. The application must be designed to handle eventual consistency to avoid reading stale data after a failover. Option C is correct: adding a second cluster in a different zone (within the same region or a different region) and enabling replication provides redundancy. If the primary cluster fails, the secondary cluster can serve requests. Option D is correct: the application must be configured to route traffic to the secondary cluster in case of primary failure. This can be achieved by using Cloud Bigtable's built-in failover mechanism or by implementing client-side routing logic. Without this routing, traffic would still be directed to the failed primary cluster, causing downtime.

Answer

Enable synchronous replication between clusters.

Answer

Take a full backup of the table to Cloud Storage daily.

Question 7

A Cloud SQL for PostgreSQL instance is experiencing high read traffic. You need to offload read queries and ensure the solution can survive a regional outage. What should you do?

Accepted Answer

Create a cross-region read replica and direct read traffic to it.. Cross-region read replicas serve read traffic and provide disaster recovery if the primary fails. Creating a cross-region read replica reduces read load and can be promoted if the primary region fails. Option D is correct. Option A (Cloud Memorystore cache) reduces latency but does not survive a regional outage. Option B (increasing machine type) helps performance but not regional failover. Option C (same-region read replica) does not survive a regional outage.

Answer

Set up Cloud Memorystore as a cache in front of the database.

Answer

Increase the machine type of the primary instance to handle the load.

Answer

Create a read replica in the same region and use it for read queries.

Question 8

A development team uses Cloud Spanner and needs to add a new index to a table with 10 TB of data. They require that the operation does not block writes or cause downtime. Which approach should they take?

Accepted Answer

Execute 'CREATE INDEX' statement; Spanner will build the index in the background without blocking.. Cloud Spanner supports online schema changes, including CREATE INDEX, which build in the background without blocking reads or writes to the table. This is a core differentiator of Spanner's distributed architecture, allowing index creation on large tables without downtime. The operation is transparent to applications and does not require a maintenance window.

Answer

Create a new table with the index and batch copy data from the original table.

Answer

Schedule a maintenance window, then create the index during the window.

Answer

Drop the table and recreate it with the index, then restore from backup.

Question 9

A company is using Cloud Firestore to store user profiles. They need to query users by both their 'age' and 'city' fields. What must they configure to perform this query efficiently?

Accepted Answer

Create a composite index on age and city.. Firestore requires a composite index to efficiently execute queries that filter on multiple fields, such as age and city. Without a composite index, the query may fail or perform poorly because Firestore automatically indexes single fields but not combinations. Creating a composite index on age and city enables the query to be served efficiently.

Answer

Use Firestore in Datastore mode for automatic composite indexes.

Answer

Configure index exemptions for the fields.

Answer

No configuration needed; single-field indexes are sufficient.

Question 10

A Cloud Bigtable instance is experiencing high read latency. The team suspects hot spotting on a single node. Which tool should they use to identify the hotspot?

Accepted Answer

Key Visualizer. Key Visualizer is the correct tool because it is specifically designed to analyze access patterns in Cloud Bigtable and identify hot spotting—where a small range of row keys receives a disproportionate amount of traffic. It visualizes read and write heatmaps across row key space and time, allowing teams to pinpoint the exact keys causing the hotspot. Unlike general-purpose monitoring tools, Key Visualizer provides row-key-level granularity essential for diagnosing hot spotting.

Answer

Cloud Logging to review request logs

Answer

Bigtable Admin API to list tables

Answer

Cloud Monitoring (Stackdriver) to check CPU utilization

Question 11

A Cloud Memorystore for Redis instance is running out of memory. The team wants to automatically remove the least recently used keys when memory is full. Which eviction policy should they configure?

Accepted Answer

allkeys-lru. The `allkeys-lru` eviction policy is correct because it applies the LRU (Least Recently Used) algorithm to all keys in the Redis instance, not just those with an expiry set. This ensures that when memory is full, the least recently accessed keys are automatically removed, regardless of whether they have a TTL, which directly meets the requirement to free memory without manual intervention.

Answer

volatile-lru

Answer

volatile-ttl

Answer

noeviction

Question 12

A company has a Cloud Bigtable cluster using HDD storage. They are migrating to a workload that requires lower latency, so they need to switch to SSD storage. How should they accomplish this?

Accepted Answer

Create a new Bigtable cluster with SSD storage in the same instance, replicate data, then delete the old cluster.. Cloud Bigtable does not support in-place conversion of storage type from HDD to SSD. The proper migration path is to create a new cluster with SSD storage within the same instance, enable replication to keep data synchronized, and then delete the old HDD cluster. This approach minimizes downtime and ensures data consistency.

Answer

Add more nodes to the existing cluster to improve latency.

Answer

Export data to Avro files, create a new SSD cluster, and import the data.

Answer

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

Question 13

A Cloud SQL for MySQL instance is being used for a production application. The team wants to implement a disaster recovery plan that can recover from a regional outage with minimal data loss and automatic failover. Which three steps should they take? (Choose THREE.)

Accepted Answer

Enable automated backups with a suitable retention period.. Automated backups in Cloud SQL for MySQL provide a baseline for disaster recovery by creating daily backups that can be restored to a new instance. With a suitable retention period, you can recover from data corruption or accidental deletion, though backups alone do not provide automatic failover or minimal data loss during a regional outage.

Answer

Create a read replica in the same region.

Answer

Increase the storage size to accommodate future growth.

Question 14

An engineer is managing a Cloud Spanner database and needs to add a new column to an existing table without downtime. Which approach should be used?

Accepted Answer

Use ALTER TABLE ADD COLUMN statement. In Cloud Spanner, adding a new column to an existing table without downtime is achieved using the ALTER TABLE ADD COLUMN statement. This DDL operation is applied online, meaning the table remains fully available for reads and writes during the schema change, with no need for data migration or table recreation.

Answer

Export the database, modify the schema, and import using Dataflow

Answer

Use CREATE INDEX for the new column

Answer

Drop and recreate the table with the new column

Question 15

An e-commerce application uses Firestore in Native mode. The team needs to run a query that filters on two fields and orders by a third field. What is the correct approach to ensure this query runs efficiently?

Accepted Answer

Create a composite index on the three fields. Firestore requires a composite index for queries that filter on multiple fields and order by a different field, because single-field indexes cannot satisfy the combined filtering and ordering constraints. Creating a composite index on the three fields (the two filter fields and the order field) allows Firestore to efficiently execute the query without scanning all documents.

Answer

Rely on automatic single-field indexes

Answer

Use an index exemption on the fields

Answer

Use Firestore in Datastore mode instead