PCDE Practice Test 2 — 10 Questions

Question 1

A financial services company is migrating a legacy on-premises OLTP application to Google Cloud. The application requires high transaction rates (thousands per second), strict ACID compliance, and the ability to scale horizontally across multiple regions with strong consistency. Which Google Cloud database service should the company choose?

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

Accepted Answer

Cloud Spanner. Cloud Spanner is a globally distributed, horizontally scalable relational database service that provides ACID transactions and strong consistency across regions. It is ideal for OLTP workloads that require high throughput, consistency, and global scalability.

Answer

Bigtable

Answer

Cloud SQL for PostgreSQL

Answer

Firestore

Question 2

A data analyst needs to run a one-time SQL query on a dataset stored in CSV files in Cloud Storage. The query will scan the entire dataset, and the analyst wants to minimize cost. Which Google Cloud service should they use?

Accepted Answer

BigQuery. BigQuery can query external data directly from Cloud Storage; using query-on-demand billing, they only pay for the data scanned. It is serverless and requires no infrastructure.

Answer

Cloud SQL

Answer

Dataproc

Answer

Cloud Spanner

Question 3

A company runs a MySQL database on-premises and wants to migrate to Cloud SQL with minimal downtime. They have a multi-terabyte database. Which migration method is most appropriate?

Accepted Answer

Use Database Migration Service with continuous replication.. Database Migration Service (DMS) supports continuous replication and minimal downtime for large databases. It handles initial snapshot and ongoing CDC.

Answer

Use Cloud SQL's import feature from a CSV file.

Answer

Take a physical backup and restore to Cloud SQL.

Answer

Use mysqldump to export and then import into Cloud SQL.

Question 4

An e-commerce platform uses Cloud Spanner as its database. The orders table has a monotonically increasing order_id as the primary key, and the team observes high write latency during peak hours. Which design change would BEST distribute write load across nodes?

Accepted Answer

Change the primary key to a UUID string. Using a UUID (or a hash prefix) as the primary key or as a leading part of a composite key prevents hotspotting on a single tablet server by distributing writes across the cluster.

Answer

Add a secondary index on order_id

Answer

Increase the number of nodes

Answer

Use interleaving with a parent table

Question 5

Refer to the exhibit. This DDL is used to create a table in Cloud Spanner. The table will be used for storing user data with high write throughput. What is one performance issue with this table design?

Accepted Answer

The primary key is a monotonically increasing integer. Using a monotonically increasing integer as the primary key in Cloud Spanner causes all writes to be directed to a single split (tablet), creating a hotspot that severely limits write throughput. Cloud Spanner distributes splits across nodes based on key ranges, and sequential keys prevent this distribution, leading to performance degradation under high write load.

Answer

The Name column is of type STRING(MAX)

Answer

There are no secondary indexes

Answer

The table is not interleaved with another table

Question 6

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 7

A team wants to create a Cloud Spanner database backup and store it in a Cloud Storage bucket for long-term archival. Which method should they use?

Accepted Answer

Use the gcloud spanner databases backup command to create a backup that resides in Cloud Storage.. Cloud Spanner provides database-level backups directly to Cloud Storage in Avro + Protobuf format. Export/import is for migration, not archival backups.

Answer

Use gcloud spanner instances create-backup to create a backup of the instance.

Answer

Take a snapshot of the Spanner instance using Cloud Storage snapshots.

Answer

Use the gcloud spanner databases export command to export to Cloud Storage.

Question 8

A Cloud Spanner database is experiencing increased read traffic. You need to add an index to improve query performance without downtime. What is the correct approach?

Accepted Answer

Use the CREATE INDEX statement. Spanner creates indexes online without blocking writes or reads.

Answer

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

Answer

Use the ALTER TABLE statement to add the index as a constraint.

Answer

Create a secondary index using the 'CREATE INDEX WITH OFFLINE' option to avoid blocking.

Question 9

A Memorystore for Redis instance is running out of memory. The application uses Redis as a cache with key expiration. You want to prevent data loss for keys that have not reached their TTL. Which eviction policy should you configure?

Accepted Answer

volatile-lru

Answer

noeviction

Answer

volatile-ttl

Answer

allkeys-lru

Question 10

Which TWO statements about Cloud Spanner schema changes are correct? (Choose 2)

Accepted Answer

Schema changes are applied asynchronously and may take minutes to hours to complete.

Answer

Schema changes require the instance to be restarted.

Answer

You can only add columns, not drop them.

Answer

Creating a secondary index requires taking the table offline.