PCDE Practice Test 22 — 15 Questions

Question 1

During a MySQL to Cloud SQL migration using Database Migration Service, the full dump phase is taking much longer than expected. The source MySQL database is 500 GB and the Cloud SQL instance is of sufficient size. What is the most likely cause of the slow dump?

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

Accepted Answer

The source database has many MyISAM tables.. Without --single-transaction, mysqldump locks tables, causing contention and slow performance. DMS uses mysqldump internally and requires InnoDB tables with --single-transaction for consistent non-blocking dumps.

Answer

The source database is using a public IP address.

Answer

Binary logging is not enabled on the source.

Answer

The Cloud SQL instance is using a shared-core machine type.

Question 2

A company uses AlloyDB for PostgreSQL for their operational database. They want to ensure automatic failover with the shortest possible RTO. Which configuration should they use?

Accepted Answer

Deploy a multi-zone AlloyDB cluster with automatic failover enabled. AlloyDB provides automatic failover with RTO under 60 seconds. Cross-zone failover in a multi-zone cluster provides the best availability within a region. Cross-region replication is not automatic and requires manual promotion. Basic instances offer no HA. Read pool failover is not automatic.

Answer

Deploy a single-zone AlloyDB cluster with a read pool

Answer

Configure a cross-region read replica and set up automated promotion scripts

Answer

Use an AlloyDB basic (single-node) instance

Question 3

A company uses Cloud SQL for MySQL and wants to define backup retention policies for compliance. Which TWO statements about Cloud SQL backup retention are correct? (Choose 2)

Accepted Answer

The maximum retention period for automated backups is 365 days.. Cloud SQL supports up to 365 automated backups and allows setting retention days up to 365. Point-in-time recovery also has a configurable retention.

Answer

Point-in-time recovery logs are retained for a maximum of 7 days.

Answer

Automated backups are retained for a minimum of 7 days.

Answer

Backups are always stored in the same region as the database.

Question 4

A company uses Cloud Spanner with a single-region configuration in us-central1. They need to improve disaster recovery to meet an RPO of zero and an RTO of less than 5 seconds across regions. Which three actions should they take? (Choose three.)

Accepted Answer

Use backup/restore to migrate data from the single-region instance to the new multi-region instance. To achieve RPO=0 and RTO<5s across regions, you need a multi-region Spanner configuration with synchronous replication. You cannot achieve cross-region RPO=0 with a single-region instance. Therefore, you must migrate to a multi-region configuration. The steps include: 1) Create a new multi-region instance (e.g., nam6) with the desired config, 2) Migrate data from the single-region instance to the multi-region instance (e.g., using backup/restore or Dataflow), 3) Update application connection strings to point to the new instance. Optionally, you can perform a rolling migration to minimize downtime. Using cross-region read replicas is not possible for Spanner (Spanner does not have read replicas in the same sense; it uses replica types within an instance).

Answer

Add a cross-region read replica to the existing single-region instance

Answer

Enable point-in-time recovery (PITR) with 7-day retention

Question 5

A company uses Cloud Spanner in a multi-region configuration with the leader region in us-central1. They want to improve write latency for users in Europe. The application's writes are latency-sensitive and must be strongly consistent. Which action should the engineer take?

Accepted Answer

Change the leader region to a European region, such as europe-west1.. In Spanner multi-region, the leader region determines where writes are committed. To reduce write latency for European users, set the leader region to a European region (e.g., europe-west1). All writes will be committed in that region, reducing round-trip time for European clients. This does not affect consistency; Spanner still provides strong consistency globally. Adding more read replicas in Europe does not affect write latency. Moving the application to Cloud SQL or Bigtable does not provide the same global strong consistency or may not meet requirements.

Answer

Add more read-only replicas in the European region.

Answer

Use a regional Spanner instance in Europe and replicate data asynchronously to the multi-region instance.

Answer

Migrate the workload to Cloud Bigtable with replication.

Question 6

A financial application requires zero data loss (RPO=0) and automatic failover within 60 seconds in the event of a zone failure. The database must support ACID transactions. Which Google Cloud service meets these requirements?

Accepted Answer

Cloud SQL with HA configuration. Cloud SQL with HA configuration uses synchronous replication to a standby instance in a different zone. If the primary zone fails, Cloud SQL automatically fails over to the standby. Because replication is synchronous, RPO is effectively zero. Automatic failover typically completes within 60 seconds.

Answer

Cloud SQL cross-region read replica

Answer

Cloud SQL single-zone instance with automatic backups

Answer

Cloud Bigtable multi-cluster replication

Question 7

A company is migrating a PostgreSQL database to AlloyDB using DMS. They need to test the converted stored procedures. Which tool should they use to write and run unit tests for PL/pgSQL functions?

Accepted Answer

pgTAP. pgTAP is a unit testing framework for PostgreSQL that allows writing tests in SQL/PL/pgSQL. It is suitable for testing stored procedures.

Answer

Cloud SQL Insights

Answer

pgAdmin

Answer

pg_stat_statements

Question 8

A company wants to migrate a 10 TB Redshift data warehouse to BigQuery with minimal downtime. Which combination of services should they use?

Accepted Answer

Use BigQuery Data Transfer Service for Redshift for initial and incremental loads.. BigQuery Data Transfer Service can directly load data from Redshift. Schema Conversion Tool (SCTS) helps convert DDL. For minimal downtime, an initial load plus CDC or incremental loads can be used.

Answer

Use DMS with a Redshift source endpoint.

Answer

Export Redshift data to CSV and load using bq load.

Answer

Use Cloud Dataflow to stream from Redshift to BigQuery.

Question 9

A company is migrating a MySQL database to Cloud SQL using Database Migration Service (DMS). The source database is on-premises and uses InnoDB tables. The migration job is configured as continuous (CDC). After starting the job, the full dump phase completes successfully, but the CDC phase shows no replicated changes. What is the most likely cause?

Accepted Answer

The source database does not have binary logging enabled.. Continuous CDC replication in DMS requires binary logging to be enabled on the source database. If binary logging is disabled, DMS cannot capture change data. The full dump works because it uses mysqldump, which does not rely on binary logs.

Answer

The Cloud SQL destination does not have public IP connectivity.

Answer

The source database is using MyISAM tables instead of InnoDB.

Answer

The DMS migration job was configured as one-time instead of continuous.

Question 10

A team uses Cloud Build to build a container image using Kaniko. They want to cache layers to speed up subsequent builds. What should they configure in their cloudbuild.yaml to enable Kaniko layer caching?

Accepted Answer

Set --cache=true and specify --cache-repo in the Kaniko builder step. Kaniko does not rely on Docker's layer caching mechanism. Instead, it uses its own remote caching system where layers are pushed to a container registry. To enable this, you must pass `--cache=true` to the Kaniko builder to instruct it to cache intermediate layers, and `--cache-repo` to specify the target repository (e.g., a registry path) where those cached layers will be stored. This allows subsequent builds to reuse previously built layers, significantly reducing build time.

Answer

Use Docker layer caching with docker build --cache-from

Answer

Set substitution variable _KANIKO_CACHE=true

Answer

Enable Cloud Build cache via the caching service

Question 11

A media company uses Cloud Bigtable to serve user recommendations with low latency. They want to implement disaster recovery with a secondary cluster in a different region. They need automatic failover without manual DNS changes. Which routing policy should they configure?

Accepted Answer

Configure read-failover routing policy and use Cloud DNS health checks. The read-failover policy uses health checks to automatically route traffic to the secondary cluster if the primary becomes unhealthy. Any-replica sends requests to the closest cluster regardless of health. Manual DNS changes would be required for any-replica after a failure. Application-managed routing is not a built-in Bigtable feature.

Answer

Enable any-replica routing policy on the Bigtable cluster

Answer

Use single-cluster routing with manual DNS failover

Answer

Implement application-managed routing with a custom health check

Question 12

A company runs a critical application on AlloyDB with a primary instance and a read pool. They want to achieve the fastest possible automatic failover during a zone outage, with minimal data loss. What is the expected RTO and RPO for AlloyDB's automatic failover within the same region?

Accepted Answer

RTO < 30 seconds, RPO ~ 0. AlloyDB provides automatic failover to a standby node within the same region, typically completing in under 30 seconds. Replication is synchronous within the region, so RPO is zero (no data loss).

Answer

RTO < 5 minutes, RPO ~ 1 second

Answer

RTO < 60 seconds, RPO ~ 0

Answer

RTO < 30 seconds, RPO < 1 minute

Question 13

An organization needs to store backup copies of a Cloud Spanner database for a minimum of 365 days to comply with regulatory requirements. Which backup option should they use?

Accepted Answer

Create a Spanner backup and set the expiration to 365 days. Cloud Spanner backups can be configured with expiration up to 365 days (max). Import/export to Cloud Storage is not a managed backup solution and does not support PITR. Bigtable backups are for Bigtable, not Spanner. Cloud SQL backups are for Cloud SQL.

Answer

Enable point-in-time recovery (PITR) with a 365-day retention period

Answer

Export the database to Cloud Storage using the gcloud command and set a lifecycle policy

Answer

Use Cloud SQL for PostgreSQL with automated backups set to 365 days

Question 14

A financial services firm runs a multi-region Spanner instance with the nam-eur-asia1 configuration. They need to ensure that if the leader region (us-central1) becomes unavailable, failover to another region occurs automatically within 1 minute. What is the expected RPO and RTO for this scenario?

Accepted Answer

RPO ~ 15 seconds, RTO < 1 minute. Spanner multi-region configurations provide automatic failover with RTO under 1 minute. For the nam-eur-asia1 configuration, it is a multi-region with multiple read-write replicas. The RPO is approximately 15 seconds because Spanner uses quorum-based replication; in the event of a region failure, a small number of recent transactions may be uncommitted.

Answer

RPO ~ 0, RTO ~ 15 seconds

Answer

RPO ~ 1 hour, RTO ~ 5 minutes

Answer

RPO = 0, RTO < 1 minute

Question 15

A company needs to choose a Google Cloud database for a globally distributed application that requires strong consistency across continents and an SLA of 99.999% for availability. Which database service meets these requirements?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only Google Cloud database that provides global strong consistency and a 99.999% availability SLA when using a multi-region configuration. Bigtable offers only eventual consistency across regions, Cloud SQL is regional, and Firestore provides strong consistency only within a single region.

Answer

Cloud Bigtable

Answer

Cloud SQL

Answer

Firestore