PCD Practice Test 30 — 15 Questions

Question 1

Refer to the exhibit. Which schema or index change would most improve this query?

Accepted Answer

Create a secondary index on Orders.CustomerID and Customers.CustomerID. Creating secondary indexes on both `Orders.CustomerID` and `Customers.CustomerID` allows Spanner to perform an index-based join without scanning the full base tables. Spanner uses distributed, strongly consistent secondary indexes to avoid full table scans, which dramatically reduces latency and resource consumption for join queries. Without these indexes, Spanner must perform a broadcast join or a full table scan on both tables, which is inefficient at scale.

Answer

Create a primary key on CustomerID

Answer

Rewrite the query as a subquery

Answer

Increase the number of Spanner nodes

Question 2

A company plans to migrate an on-premises Oracle database to Cloud SQL for PostgreSQL. They need to minimize downtime and ensure continuous sync during migration. Which migration approach should they use?

Accepted Answer

Use DMS with a continuous migration job, allowing CDC replication until cutover.. Database Migration Service (DMS) with a continuous migration job enables ongoing Change Data Capture (CDC) replication from the source Oracle database to Cloud SQL for PostgreSQL. This approach keeps the target database synchronized with minimal downtime, allowing a controlled cutover when the migration is complete. It is the only option that satisfies the requirements of continuous sync and minimal downtime.

Answer

Export the Oracle database as a dump file and import it into Cloud SQL manually.

Answer

Use DMS with a one-time migration job, then manually sync changes before cutover.

Answer

Use Cloud SQL Auth Proxy to connect Oracle to Cloud SQL and replicate data using a custom script.

Question 3

A company uses AlloyDB for PostgreSQL and needs to scale read traffic automatically. They also want to ensure the database remains available if the primary zone fails. Which two features should they use? (Choose two.)

Accepted Answer

Configure the cluster as a regional cluster with high availability. Option C is correct because configuring the AlloyDB cluster as a regional cluster with high availability provisions a primary instance and a standby replica in a different zone within the same region, enabling automatic failover if the primary zone fails. Option E is correct because a read pool instance with autoscaling enabled automatically adds or removes read replicas based on CPU and memory utilization, which directly addresses the need to scale read traffic automatically. Option A is incorrect because AlloyDB Omni is a self-managed on-premises or local deployment and does not provide Google Cloud's managed HA or autoscaling read pools. Option B is incorrect because a single-zone cluster offers no zone-level redundancy, so read replicas do not provide high availability for the primary. Option D is incorrect because cross-region replication is for disaster recovery and lower-latency reads in other regions, not for automatic read scaling or primary-zone failover within a region.

Answer

Deploy AlloyDB Omni on-premises

Answer

Use a single-zone cluster and rely on read replicas for HA

Answer

Enable cross-region replication

Question 4

A developer wants to store application logs from Compute Engine instances in a centralized logging system. Which service should they use?

Accepted Answer

Cloud Logging. Cloud Logging is Google Cloud's fully managed, centralized log management service designed to ingest, store, search, analyze, and alert on log data from all GCP resources, including Compute Engine instances. The Cloud Logging agent (or Ops Agent) running on each VM forwards application and system logs to Cloud Logging, where they become accessible via the Logs Explorer, Log Router, and log-based metrics. This directly satisfies the requirement to store application logs from Compute Engine instances in a centralized system.

Answer

Cloud Monitoring

Answer

Cloud Trace

Answer

Cloud Debugger

Question 5

You are deploying a Python Cloud Function using the Google Cloud CLI. The deployment fails with 'ERROR: (gcloud.functions.deploy) ResponseError: status=[404], code=[OK], message=[The function ... does not exist]' but the function already exists. What is the most likely cause?

Accepted Answer

The gcloud config's region does not match the region where the function was deployed.. The 404 error indicates the deployment command cannot locate the function in the specified region. When you deploy a Cloud Function using the gcloud CLI, the command uses the default region set in your gcloud configuration (or the --region flag). If the function was originally deployed in a different region, the CLI will look for it in the wrong region and fail with a 404, even though the function exists elsewhere. This is the most common cause of this specific error message.

Answer

The function was already deployed with the same name, causing a conflict.

Answer

The Python runtime version is not supported in that region.

Answer

The Cloud Functions API is not enabled.

Question 6

A company needs to run hybrid transactional/analytical processing (HTAP) workloads on a PostgreSQL-compatible database. They want to use in-database ML inference and require 4x faster OLTP performance compared to standard PostgreSQL. Which database should they choose?

Accepted Answer

AlloyDB for PostgreSQL. AlloyDB for PostgreSQL is Google Cloud's PostgreSQL-compatible database engineered for HTAP workloads, offering 4x faster OLTP than standard PostgreSQL, columnar engine acceleration for analytics, and built-in ML inference via integration with Vertex AI. It uniquely satisfies all three requirements in the question.

Answer

BigQuery

Answer

Cloud SQL for PostgreSQL

Answer

Cloud Spanner

Question 7

A developer is setting up a Cloud Build configuration file for a Node.js application. They want to ensure that build steps are executed only when changes are pushed to the 'main' branch. What is the correct approach?

Accepted Answer

Use a build trigger with a branch filter. Cloud Build triggers can be configured with a branch filter (e.g., `^main$`) that ensures builds are only initiated when changes are pushed to the specified branch. This is the native, declarative way to control build execution based on Git branch events, without requiring custom scripting or external scheduling.

Answer

Use a script in the build step to check the branch name

Answer

Use Cloud Scheduler to trigger builds based on time intervals

Answer

Use a condition in the build config file

Question 8

A company needs to migrate an on-premises Cassandra database to Google Cloud. They want a managed NoSQL database with high availability and low latency. Which service should they choose?

Accepted Answer

Cloud Bigtable. Cloud Bigtable is Google Cloud's fully managed, petabyte-scale NoSQL wide-column database, which makes it the natural target for a Cassandra migration because both use a similar wide-column data model and are optimized for high-throughput, low-latency reads/writes on massive datasets. Bigtable provides automatic replication across zones/regions for high availability and consistent single-digit-millisecond latency at scale, matching the stated requirements.

Answer

Cloud SQL

Answer

Cloud Spanner

Answer

Firestore

Question 9

An engineer notices high CPU utilization on a Cloud Spanner instance and wants to identify the queries consuming the most resources. Which tool should they use?

Accepted Answer

Query Insights for Spanner.. Query Insights for Spanner is the purpose-built tool that surfaces query-level statistics including CPU consumption, latency, and execution counts, allowing engineers to identify the top resource-consuming queries. It integrates with Cloud Monitoring and provides per-query drill-downs that directly answer the question.

Answer

Cloud Monitoring (Stackdriver) dashboards for Spanner.

Answer

Key Visualizer for Bigtable.

Answer

Cloud Logging with query logs.

Question 10

A company has an AlloyDB cluster in us-central1. They want to replicate data to a secondary region for disaster recovery with a recovery point objective (RPO) of less than 1 second. Which AlloyDB feature should they use?

Accepted Answer

Create a cross-region read replica in the secondary region. AlloyDB supports cross-region replication for disaster recovery using cross-region read replicas (also known as cross-region clusters). These replicas maintain an asynchronous copy of the primary cluster in a secondary region, enabling an RPO of less than 1 second. AlloyDB Omni (option A) is intended for on-premises or other cloud deployments, not for cross-region replication within GCP. Export/import (option B) cannot achieve sub-second RPO, and Cloud SQL for PostgreSQL (option C) is a different service. Therefore, option D is the correct feature.

Answer

Use AlloyDB Omni to replicate to an instance in the secondary region

Answer

Export the database to Cloud Storage and import in the secondary region

Answer

Configure a Cloud SQL for PostgreSQL read replica in the secondary region

Question 11

A company needs to analyze terabytes of log data for business intelligence. The queries are complex SQL aggregations and run periodically. The data is read-only after ingestion. Which Google Cloud database is most suitable?

Accepted Answer

BigQuery. BigQuery is the correct choice because it is a serverless, highly scalable data warehouse designed for petabyte-scale analytics using SQL. It excels at complex aggregations over terabytes of read-only log data, with automatic partitioning and columnar storage that optimize query performance for periodic analytical workloads.

Answer

Cloud SQL

Answer

Cloud Spanner

Answer

Cloud Bigtable

Question 12

A team is using Cloud Trace to analyze performance of a microservices application. They notice that some spans are missing from the trace. What is the most likely cause?

Accepted Answer

The trace sampling rate is set too low. The most likely cause of missing spans in Cloud Trace is that the trace sampling rate is set too low. Cloud Trace uses a configurable sampling rate to control how many requests are traced; if the rate is low, many requests are not sampled, resulting in incomplete traces. This is a common configuration issue, not a failure to send traces or a network problem.

Answer

The application is not sending traces for all services

Answer

There is a network latency issue

Answer

The Cloud Trace API is disabled for some projects

Question 13

A company uses Firestore for a mobile app. They want to implement security rules that allow users to create documents only if they are authenticated and the document's 'owner' field matches their UID. Additionally, they want to allow reads of any document where the 'visibility' field is 'public'. Which TWO conditions should the rules include?

Accepted Answer

allow read: if resource.data.visibility == 'public';. Option E is correct because it combines both required conditions for document creation: request.auth.uid != null verifies the user is authenticated, and request.resource.data.owner == request.auth.uid ensures the incoming document's owner field matches the user's UID, which is exactly what the scenario demands for create operations. Option D is correct because reads of existing documents must be evaluated against the stored document data, so resource.data.visibility == 'public' properly grants read access when the persisted visibility field equals 'public'. Option A is incorrect because it omits the authentication check, allowing unauthenticated requests with a matching owner value to create documents. Option B is incorrect because request.resource.data refers to the incoming write payload, not the stored document, so it cannot correctly gate read operations on existing data. Option C is incorrect because it only checks authentication for all writes and does not enforce the owner field match, and it is overly broad by covering update and delete as well.

Answer

allow create: if resource.data.owner == request.auth.uid;

Answer

allow read: if request.resource.data.visibility == 'public';

Answer

allow write: if request.auth.uid != null;

Question 14

Refer to the exhibit. The Cloud Run service is experiencing high tail latency under moderate load. Which change would most effectively reduce latency?

Accepted Answer

Reduce containerConcurrency to 10.. High tail latency under moderate load often indicates that requests are queuing behind each other due to excessive concurrency. Reducing `containerConcurrency` to 10 limits the number of simultaneous requests each container instance handles, which reduces queueing delay and improves per-request response time. This is the most effective change because it directly controls the request multiplexing level, preventing a single instance from being overwhelmed.

Answer

Increase CPU limit to 2.

Answer

Increase containerConcurrency to 250.

Answer

Increase timeoutSeconds to 600.

Question 15

You are using Cloud Spanner and need to read data that is consistent as of a specific point in time, but you can tolerate staleness up to 10 seconds. Which read type should you use to achieve the best performance?

Accepted Answer

Stale read with a staleness bound of 10 seconds. A stale read with a staleness bound of 10 seconds allows Cloud Spanner to serve the read from any replica that has data within that staleness window, avoiding the latency of a strong read that must contact the leader. This provides the best performance while still guaranteeing consistency as of a point in time up to 10 seconds ago, meeting the requirement of tolerating staleness up to 10 seconds.

Answer

Partitioned read

Answer

Read with a timestamp bound exactly 10 seconds in the past

Answer

Strong read