PCD Practice Test 15 — 15 Questions

Question 1

You need to migrate an Oracle database to Cloud SQL for PostgreSQL. The schema must be converted using Oracle to PostgreSQL migration tools. Which tool should you use to automate schema conversion?

Accepted Answer

Ora2Pg. Ora2Pg is an open-source tool for converting Oracle schemas, data, and procedures to PostgreSQL.

Answer

Cloud Dataflow

Answer

pg_dump

Answer

Database Migration Service (DMS)

Question 2

A company runs a global e-commerce platform on GKE. They need to serve users with low latency from multiple regions. Which load balancing solution should they use?

Accepted Answer

Global external HTTP(S) Load Balancer. A global external HTTP(S) Load Balancer is the correct choice because it provides a single anycast IP address that routes traffic from users worldwide to the nearest GKE backend, minimizing latency. It supports cross-regional failover and integrates with Cloud CDN for caching static content, making it ideal for a global e-commerce platform. Regional load balancers cannot serve traffic across multiple regions with a single IP, which is required for global low-latency access.

Answer

Regional external HTTP(S) Load Balancer

Answer

Internal TCP/UDP Load Balancer

Answer

SSL Proxy Load Balancer

Question 3

A company runs a batch job that processes large files from Cloud Storage every night. The job must complete within a 2-hour window. If the job fails, it should retry automatically. Which Google Cloud service should they use to orchestrate this job?

Accepted Answer

Cloud Composer. Cloud Composer (D) is the correct choice because it is a fully managed workflow orchestration service built on Apache Airflow, designed to schedule, monitor, and retry batch jobs with complex dependencies. It can trigger a Cloud Storage file processing job, enforce a 2-hour execution window, and automatically retry on failure using Airflow's built-in retry mechanisms and SLA monitoring.

Answer

Compute Engine with startup script

Answer

Cloud Run

Answer

App Engine Cron

Question 4

A developer is building an event-driven system using Cloud Pub/Sub. They need to ensure reliable message delivery and processing. Which three practices should they follow?

Accepted Answer

Use pull subscriptions with synchronous acknowledgment.. Pull subscriptions with synchronous acknowledgment (option B) ensure that a message is not acknowledged until the subscriber has successfully processed it. This prevents premature acknowledgment and message loss, because Cloud Pub/Sub will redeliver the message if the acknowledgment deadline expires without a synchronous ack. This is a core pattern for reliable processing.

Answer

Set a minimum number of delivery attempts.

Answer

Use message ordering.

Question 5

A developer is deploying an application on Compute Engine and needs to automatically apply security patches without downtime. The application runs behind a TCP load balancer. What is the best deployment strategy?

Accepted Answer

Use a rolling update on the instance group.. A rolling update on a managed instance group allows the developer to update instances incrementally, applying security patches without downtime. The TCP load balancer automatically distributes traffic only to healthy instances, so as each instance is updated and passes health checks, traffic is seamlessly redirected away from instances being patched.

Answer

Use a canary deployment with a separate instance group.

Answer

Stop all instances, apply patches, then restart them.

Answer

Use a managed instance group with autohealing.

Question 6

A company is designing a real-time leaderboard for a mobile gaming application. The leaderboard must support millions of concurrent users updating their scores and querying rankings with low latency (under 100ms). Scores change frequently and require strong consistency for reads. The development team is evaluating Cloud SQL and Cloud Spanner. They estimate they need to handle 100,000 writes per second. Which database should they choose and why?

Accepted Answer

Cloud Spanner because it provides horizontal scaling, strong consistency, and high write throughput.. Cloud Spanner is the correct choice because it provides horizontal scaling with strong consistency and can handle 100,000 writes per second while maintaining ACID transactions and low-latency reads. Unlike Cloud SQL, Spanner scales horizontally across nodes without sacrificing consistency, making it ideal for a real-time leaderboard with millions of concurrent users.

Answer

Cloud Firestore because it offers real-time synchronization and is serverless.

Answer

Cloud Bigtable because it's optimized for high write throughput and time-series data.

Answer

Cloud SQL with read replicas because it's cost-effective and supports ACID transactions.

Question 7

You deployed a new version of your application that uses Cloud Pub/Sub for asynchronous messaging. After deployment, you notice that messages are accumulating in the subscription backlog. You suspect the subscriber is too slow. Which tool should you use to diagnose?

Accepted Answer

Cloud Monitoring to check subscriber's processing latency and throughput.. Cloud Monitoring is the correct tool because it provides metrics such as subscriber processing latency, throughput, and backlog size for Pub/Sub subscriptions. By examining these metrics, you can quantify how slow the subscriber is and identify whether the issue is due to high latency or insufficient throughput, directly addressing the suspicion of a slow subscriber.

Answer

Cloud Trace to trace message processing.

Answer

Cloud Logging to view subscriber logs.

Answer

Cloud Profiler to profile subscriber code.

Question 8

A company runs a containerized application on Google Kubernetes Engine (GKE) with a regional cluster. The application experiences intermittent slowdowns during peak hours. The team notices that the number of nodes is not scaling up quickly enough. The application consists of a frontend deployment with a HorizontalPodAutoscaler (HPA) targeting 80% CPU utilization, and the cluster has a Cluster Autoscaler enabled with a maximum of 10 nodes. During a recent spike, the HPA increased replicas, but the Cluster Autoscaler was slow to add nodes, causing the new pods to remain pending. What is the most likely cause of this delay?

Accepted Answer

The Cluster Autoscaler has a built-in delay before adding nodes to avoid flapping.. The Cluster Autoscaler includes a built-in cooldown period (default 10–15 minutes) to prevent flapping—rapidly adding and removing nodes in response to transient spikes. During this delay, pending pods cannot be scheduled on new nodes, which explains why the HPA increased replicas but the new pods remained pending. This is the most likely cause given that the cluster is regional and the autoscaler is enabled.

Answer

The cluster is configured with a single zone, limiting node pool expansion.

Answer

The HPA is using a custom metric that is not supported by the Cluster Autoscaler.

Answer

The node pool's autoscaling is limited by the quota for Compute Engine resources in that zone.

Question 9

A developer needs to deploy a Cloud Run service from a container image in Artifact Registry. What IAM role should be granted to the Cloud Run service account?

Accepted Answer

roles/artifactregistry.reader. The Cloud Run service account needs permission to read the container image from Artifact Registry during deployment. The `roles/artifactregistry.reader` role grants the `artifactregistry.repositories.downloadArtifacts` permission, which is required to pull the image. Without this role, the deployment fails with an access denied error.

Answer

roles/storage.objectViewer

Answer

roles/cloudbuild.builds.builder

Answer

roles/run.invoker

Question 10

You deployed a microservice on Cloud Run. Users report intermittent 503 errors. The service uses Cloud SQL with connection pooling. What is the most likely cause?

Accepted Answer

The connection pool is drained due to CPU throttling on Cloud Run.. When Cloud Run CPU throttling occurs (e.g., during cold starts or when the instance is processing requests beyond its allocated CPU), the connection pool can become drained because existing connections are held open while new requests cannot be processed. This leads to intermittent 503 errors as the service cannot establish new database connections or respond to incoming requests in time. Connection pooling does not protect against CPU throttling; it only manages database connections efficiently.

Answer

The service is not using a VPC connector for Cloud SQL access.

Answer

The Cloud SQL auth proxy is not configured.

Answer

The Cloud Run service name is not resolvable via Cloud DNS.

Question 11

A team is migrating a legacy application database to Cloud SQL. They want to implement versioned schema changes as part of their CI/CD pipeline. Which tool should they use?

Accepted Answer

Liquibase. Liquibase is a database schema migration tool that supports version-controlled, repeatable schema changes and integrates well with CI/CD pipelines. Option B (gcloud sql import) is used for importing data, not schema versioning. Option C (Cloud Deployment Manager) is for infrastructure-as-code, not database schema migrations. Option D (Cloud Build) is a CI/CD service but does not provide built-in schema migration capabilities; Liquibase is the specialized tool for this purpose.

Answer

gcloud sql import

Answer

Cloud Deployment Manager

Answer

Cloud Build

Question 12

Match each Firebase feature to its description.

Accepted Answer

Cloud Firestore: A NoSQL document database for storing and syncing data in real time.. Firebase features include Cloud Firestore (NoSQL database), Authentication (user login), and Cloud Functions (backend code). Common confusions: mixing NoSQL vs relational, and hosting vs functions.

Answer

Cloud Firestore: A relational database with SQL queries for structured data.

Answer

Firebase Hosting: A Firebase feature for running backend code in response to events.

Question 13

Which THREE steps are required to set up a CI/CD pipeline for Cloud Run using Cloud Build and GitHub? (Choose THREE.)

Accepted Answer

Enable the Cloud Build, Cloud Run, and Artifact Registry APIs.. To set up a CI/CD pipeline for Cloud Run using Cloud Build and GitHub, three steps are required: (A) enable the Cloud Build, Cloud Run, and Artifact Registry APIs; (B) grant the Cloud Build service account permission to deploy to Cloud Run; and (C) create a cloudbuild.yaml file in the repository root. Option D is incorrect because Container Registry is deprecated and Cloud Run typically uses Artifact Registry. Mirroring the GitHub repository to Cloud Source Repositories (E) is optional, not required.

Answer

Push the container image to Container Registry.

Answer

Mirror the GitHub repository to Cloud Source Repositories.

Question 14

An engineer needs to configure Firestore security rules for a mobile app where users can only read and write their own data. The user's UID is stored in the document field 'owner'. Which rule correctly restricts access?

Accepted Answer

allow read, write: if resource.data.owner == request.auth.uid;. The correct rule uses 'resource.data.owner' to read the 'owner' field from the document and compares it to 'request.auth.uid', which represents the authenticated user's unique ID. This ensures users can only access documents where they are the owner. Option A uses 'request.auth.name', which is not a valid security rule field. Option C uses 'request.auth.userId', which is also invalid. Option D incorrectly compares 'resource.data.userId' to 'request.auth.uid', but the document field is 'owner', not 'userId'.

Answer

allow read, write: if resource.data.owner == request.auth.name;

Answer

allow read, write: if resource.data.owner == request.auth.userId;

Answer

allow read, write: if resource.data.userId == request.auth.uid;

Question 15

A development team is using Cloud Trace to analyze performance bottlenecks in a Node.js application deployed on GKE. They have enabled trace sampling at 10% and can see some traces, but many requests are not captured. They want to increase the sampling rate to 100% for a specific high-traffic endpoint while keeping the default sampling rate for other endpoints. How can they achieve this?

Accepted Answer

Implement a custom sampler in the application code to sample the specific endpoint at 100%.. Cloud Trace allows you to implement a custom sampler in your application code to override the default sampling rate for specific endpoints. By using the OpenTelemetry SDK, you can create a sampler that checks the request path and returns a sampling decision of 1.0 (100%) for the high-traffic endpoint while delegating to the default sampler (e.g., 0.1) for all other requests. This gives you fine-grained control without affecting the global sampling configuration.

Answer

Use a separate trace exporter for the high-traffic endpoint.

Answer

Increase the quota for trace spans per request.

Answer

Set the global trace sampling rate to 100% in the application configuration.