PCD Practice Test 24 — 15 Questions

Question 1

You are configuring a Cloud SQL for PostgreSQL instance for high availability. The instance must have automatic failover in under 60 seconds and avoid any data loss. Which configuration meets these requirements?

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

Accepted Answer

Create a regional HA configuration with synchronous replication. Regional HA configures a primary and a standby in different zones within the same region, using synchronous replication to ensure no data loss and failover in under 60 seconds.

Answer

Use Cloud Spanner instead

Answer

Create a zonal HA configuration with asynchronous replication

Answer

Add a cross-region read replica and promote it on failure

Question 2

A financial services company needs a globally distributed relational database with strong ACID transactions and high availability across regions. They anticipate unpredictable traffic spikes and need to pay only for the resources they use. Which Google Cloud database and scaling approach is most suitable?

Accepted Answer

Cloud Spanner with processing units and auto-scaling. Cloud Spanner provides global distribution, strong consistency, and ACID transactions. With fine-grained scaling using processing units and auto-scaling, it can automatically adjust capacity based on demand, optimizing cost.

Answer

Cloud SQL for PostgreSQL with cross-region replication

Answer

Bigtable with replication

Answer

Cloud Spanner with node-based scaling and manual resizing

Question 3

Which Cloud SQL setting ensures that all client connections to the database use SSL?

Accepted Answer

Set the 'require_ssl' flag to 'on'.. The 'require_ssl' flag in Cloud SQL enforces SSL connections. If enabled, non-SSL connections are rejected. IAM database authentication controls login via IAM but does not mandate SSL. Private IP alone does not enforce SSL; it's still possible to connect without SSL over the private network.

Answer

Use private IP only.

Answer

Set the 'ssl_mode' to 'required'.

Answer

Enable IAM database authentication.

Question 4

What is the first step to resolve this error?

Accepted Answer

Add a null check on line 45.. The error is a NullReferenceException, which occurs when code attempts to access a member of a null object. Adding a null check on line 45 prevents the exception by ensuring the object is not null before use, which is the standard first step in debugging such runtime errors in managed code environments like .NET or Java.

Answer

Roll back the deployment.

Answer

Restart the service.

Answer

Increase memory for the service.

Question 5

Match each command-line tool to its primary use.

Accepted Answer

gcloud: Primary interface for Google Cloud Platform. The correct matches are: gcloud for general GCP management, gsutil for Cloud Storage, kubectl for Kubernetes, and bq for BigQuery. Common confusions include mixing up gcloud with gsutil, or kubectl with bq.

Answer

gcloud: Manage Cloud Storage buckets and objects

Answer

kubectl: Run queries and manage BigQuery datasets

Question 6

A financial services company is migrating a critical PostgreSQL database to AlloyDB using Database Migration Service (DMS). They want to minimize downtime by using continuous change data capture (CDC). After the initial full dump, what phase must be completed before promoting the replica to primary?

Accepted Answer

Complete the CDC phase. DMS provides a CDC phase that continuously replicates changes from the source to the destination. Only after the replica catches up and the application can be stopped can you promote the replica. The full dump is the first step, then CDC ensures consistency.

Answer

Perform a final manual sync

Answer

Take a new full dump

Answer

Delete all existing data in AlloyDB

Question 7

An administrator runs the above command to create a Compute Engine instance. However, the nginx service does not start. What is the most likely cause?

Accepted Answer

The instance has no external IP address and cannot reach the internet to download packages.. The command likely creates a Compute Engine instance without specifying an external IP address (e.g., using `--no-address` or omitting `--address`). Without an external IP, the instance cannot reach the internet to download the nginx package from repositories, causing the startup script that installs and starts nginx to fail. This is the most direct cause of the nginx service not starting.

Answer

The metadata key is misspelled; it should be 'startup-script-url'.

Answer

The instance does not have the compute.instance.update permission.

Answer

The startup script runs before the boot disk is fully mounted.

Question 8

An organization is migrating a MySQL database to Cloud SQL for MySQL using Database Migration Service. The migration job is in the 'Full dump + CDC' phase. After a successful full dump, the CDC phase is replicating changes. To complete the migration with minimal downtime, what should the engineer do?

Accepted Answer

Promote the Cloud SQL instance using the DMS console or API, which triggers a short cutover window.

Answer

Wait for the CDC phase to automatically complete and promote.

Answer

Stop the application, then promote the Cloud SQL instance to make it the primary.

Answer

Delete the source database and then promote the Cloud SQL instance.

Question 9

A company wants to use BigQuery Omni to query data stored in Amazon S3. They have set up a BigQuery Omni connection. Which querying method should they use?

Accepted Answer

Create an external table referencing the S3 data. BigQuery Omni uses external tables stored in S3 (or Azure Blob). You create an external table that points to the S3 location, then query it with standard SQL.

Answer

Use Cloud Storage Transfer Service

Answer

Use the BigQuery Data Transfer Service to copy data

Answer

Use the bq load command to load data into BigQuery

Question 10

A company wants to back up their Cloud Spanner database for disaster recovery. They need a backup that can be restored in a different region. Which backup method should they use?

Accepted Answer

Use Spanner export to GCS. Cloud Spanner supports full database exports to GCS in Avro format. These exports can be restored to any Spanner instance, including in a different region. There are no incremental backups; only full exports.

Answer

Use Bigtable managed backups

Answer

Use Cloud SQL export

Answer

Use gcloud spanner operations backup

Question 11

A global e-commerce company uses Cloud Spanner for transactional data. They need to stream real-time order changes to a BigQuery table for analytics. Which approach meets the requirement with minimal latency and operational overhead?

Accepted Answer

Use Spanner change streams to capture changes, publish to Pub/Sub, and use Dataflow to write to BigQuery.. Cloud Spanner change streams capture incremental changes (inserts, updates, deletes) and can be read via Pub/Sub. A Dataflow pipeline can then write these changes to BigQuery in near real-time. This is the recommended pattern for streaming Spanner changes to BigQuery.

Answer

Create a Cloud Function that queries Spanner every minute and writes new records to BigQuery.

Answer

Use Cloud Scheduler to run a daily export of Spanner table to Cloud Storage, then load into BigQuery.

Answer

Configure a Datastream stream from Spanner to BigQuery.

Question 12

A company uses Datastream to replicate changes from an on-premises Oracle database to BigQuery. They need to also send the same change events to a custom application for real-time processing. Which TWO actions should they take? (Choose 2)

Accepted Answer

Configure Datastream to write to a Pub/Sub topic. Datastream can write to Pub/Sub, which then can be consumed by the application. Alternatively, Datastream can write to GCS (Avro/JSON) and then Pub/Sub or Dataflow can be used. The direct approach is to stream to Pub/Sub.

Answer

Use Datastream to write to Cloud Bigtable

Answer

Set up a Cloud Function to read from BigQuery and forward to the application

Answer

Use Dataflow to read from GCS and publish to Pub/Sub

Question 13

You are designing a cross-database solution where Cloud Spanner is the source of truth for transactional data. You need to stream all changes from Spanner to BigQuery for near-real-time analytics. Which approach should you use?

Accepted Answer

Enable Spanner change streams and read directly via Dataflow into BigQuery. Spanner change streams capture row-level changes and can be routed through Pub/Sub to a Dataflow pipeline that writes to BigQuery.

Answer

Set up a trigger in Spanner to call a Cloud Function that inserts into BigQuery

Answer

Configure Datastream to connect to Spanner and replicate to BigQuery

Answer

Use Cloud Scheduler to periodically query Spanner for new rows and insert into BigQuery

Question 14

A team is using Datastream to replicate from MySQL to BigQuery. They notice that the BigQuery table is missing some updates that occurred in the source. Which is the most likely cause?

Accepted Answer

The source MySQL binary log retention period is too short, causing log truncation before Datastream reads the changes. Datastream uses transaction logs and may skip events if the source binary logs are not retained long enough, or if there is a schema mismatch.

Answer

BigQuery does not support streaming inserts from Datastream

Answer

The Datastream connection profile uses read replicas that are lagging

Answer

Cloud SQL does not support MySQL

Question 15

A company uses a polyglot persistence architecture: Cloud SQL for transactions, Bigtable for real-time analytics, and BigQuery for reporting. They need to synchronize data from Cloud SQL to Bigtable in near real-time. Which combination of services should they use?

Accepted Answer

Datastream + Dataflow. Datastream can capture CDC from Cloud SQL (MySQL/PostgreSQL) and publish to Pub/Sub. Dataflow can then read from Pub/Sub and write to Bigtable. This provides near real-time sync.

Answer

Dataflow + Cloud SQL

Answer

Cloud Pub/Sub + Cloud Functions

Answer

Cloud Functions + BigQuery