PCD Practice Exam 63 — 20 Questions

Question 1

You are deploying a stateful application on GKE that requires persistent storage with high IOPS. You need to ensure that each pod can failover to a different node and still access the same data. Which volume type should you use?

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

Accepted Answer

PersistentVolumeClaim with ReadWriteMany.. A PersistentVolumeClaim with ReadWriteMany (RWX) is correct because it allows multiple pods to mount the same volume simultaneously, enabling pod failover to different nodes while maintaining access to the same persistent data. This is essential for stateful applications requiring high IOPS, as RWX volumes (e.g., backed by Filestore or Cloud Filestore) provide shared, concurrent read-write access across nodes in GKE.

Answer

ConfigMap.

Answer

EmptyDir.

Answer

PersistentVolumeClaim with ReadWriteOnce.

Question 2

Your Cloud Spanner database runs a query that uses a secondary index. The query plan shows an 'Index Join' operation. What can you do to eliminate this join and improve query performance?

Accepted Answer

Use the STORING clause to include the needed columns in the index. The 'Index Join' operation in Cloud Spanner occurs when a secondary index does not contain all the columns needed by the query, forcing Spanner to join the index with the base table to retrieve the missing data. By using the STORING clause (also known as covering index), you include the required columns directly in the index, allowing Spanner to satisfy the query entirely from the index without accessing the base table, thus eliminating the join and improving performance.

Answer

Change the index to a local index

Answer

Create a new interleaved table

Answer

Rewrite the query as a join

Question 3

You are designing a Bigtable schema for a financial data application that stores trade records. Each trade has a trade ID, symbol, timestamp, price, and volume. Queries include fetching all trades for a symbol in a time range. Which three row key design practices should you apply? (Choose THREE.)

Accepted Answer

Separate frequently accessed columns (price, volume) from metadata (trade ID) into different column families. Separating frequently accessed columns like price and volume from metadata like trade ID into different column families optimizes read performance. In Bigtable, column families are stored separately on disk, so queries that only need price and volume can avoid reading the trade ID column family, reducing I/O and improving latency.

Answer

Use the trade ID as the entire row key

Answer

Store all fields in a single column family

Question 4

A developer uses the above cloudbuild.yaml. The build fails with error: 'unauthorized: You don't have the permission to push to this repository.' What is the most likely cause?

Accepted Answer

The Cloud Build service account does not have Artifact Registry Writer role. The error 'unauthorized: You don't have the permission to push to this repository' indicates that the Cloud Build service account lacks the necessary IAM permissions to push the container image to Artifact Registry. By default, Cloud Build uses the default compute engine service account (PROJECT_NUMBER-compute@developer.gserviceaccount.com) or a user-specified service account, which must have the Artifact Registry Writer role (roles/artifactregistry.writer) to push images. Without this role, the push is denied regardless of the image tag, registry URL, or project ID spelling.

Answer

The image tag 'latest' is invalid

Answer

The Docker registry URL is incorrect

Answer

The project ID 'my-project' is misspelled

Question 5

A company is migrating from MySQL to Cloud SQL MySQL using Database Migration Service with continuous CDC. They want to test the migrated database with production traffic before cutting over, while still keeping the source as primary. What should they do?

Accepted Answer

Create a clone of the Cloud SQL replica for testing. DMS allows you to promote the replica to a standalone instance for testing while the CDC stream continues. However, promoting the replica stops the migration. The recommended approach is to create a clone from the replica for testing, or use a separate test environment.

Answer

Use a separate DMS job for testing

Answer

Point the application directly to the replica

Answer

Promote the replica to a standalone instance for testing

Question 6

A team deploys a microservices architecture on GKE with Istio service mesh. They want to enforce mutual TLS (mTLS) between services. After enabling Istio with the default configuration, some services report connection errors. What is the most likely cause?

Accepted Answer

Some services do not have Istio sidecar injected, so strict mTLS fails.. Istio's default configuration enables 'STRICT' mTLS mode, which requires all services to have an Envoy sidecar proxy injected to handle TLS handshakes. If any service lacks the sidecar, it cannot participate in mTLS, causing connection errors when other services attempt to communicate with it using TLS. The error typically manifests as 'upstream connect error' or 'TLS handshake failure' in the sidecar logs.

Answer

The services need a ServiceEntry to communicate with each other.

Answer

The namespace is not labeled with istio-injection=enabled.

Answer

The services are using a different service mesh protocol.

Question 7

A company uses Cloud Spanner for a globally distributed application. They need to capture all row-level changes (inserts, updates, deletes) and publish them to Pub/Sub for downstream processing. Which Spanner feature should they use?

Accepted Answer

Spanner change streams. Spanner change streams allow you to capture data changes and stream them to Pub/Sub topics for further processing. They provide a record of all mutations.

Answer

Spanner commit timestamps

Answer

Spanner mutations in Dataflow

Answer

Spanner interleaved tables

Question 8

Which TWO of the following are valid strategies for testing Cloud Functions locally before deployment?

Accepted Answer

Use the Cloud Functions emulator provided by gcloud beta emulators.. The `gcloud beta emulators` command includes a Cloud Functions emulator that allows you to run your functions locally in a simulated environment, enabling testing without deploying to the cloud. Option D is correct because the Functions Framework is an open-source library that starts a local HTTP server (typically on port 8080) and serves your function, matching the Cloud Functions runtime environment exactly.

Answer

Write unit tests that mock the HTTP request and response objects.

Answer

Use the Cloud Console to invoke the function with test events.

Answer

Deploy the function to a staging Cloud Functions project and test via HTTP invocations.

Question 9

Refer to the exhibit. A developer sees this log entry in Cloud Logging. The application is running on Compute Engine. Which tool should they use to further diagnose the cause of the connection refusal?

Accepted Answer

VPC Flow Logs to analyze network traffic.. The log entry indicates a connection refusal, which is a network-level issue. VPC Flow Logs capture metadata about network traffic to and from Compute Engine instances, including whether connections were accepted or rejected. By analyzing these logs, the developer can identify the source and destination IPs, ports, and protocol, and determine if a firewall rule or routing issue is causing the refusal.

Answer

Cloud Monitoring to check network metrics.

Answer

Cloud Profiler to identify CPU bottlenecks.

Answer

Cloud Trace to trace the request flow.

Question 10

A developer is designing a CI/CD pipeline for a Node.js application hosted on Cloud Run using Cloud Build. The pipeline should run unit tests, build the container, push to Artifact Registry, and deploy to Cloud Run. The developer wants to minimize build time by caching dependencies. What is the recommended approach?

Accepted Answer

Use Cloud Build's built-in caching with a persistent volume to store node_modules between builds.. Cloud Build supports built-in caching via persistent volumes (e.g., `/cache` or `/workspace`) that can store `node_modules` across builds. By configuring a cache volume in the `cloudbuild.yaml` and using `npm ci --prefer-offline`, the pipeline avoids re-downloading dependencies on every run, significantly reducing build time for Node.js applications on Cloud Run.

Answer

Run npm install locally and commit the node_modules folder to the repository for faster builds.

Answer

Use Cloud Build's step-level caching by copying the node_modules from a previous build step.

Answer

Create a custom base image that includes all dependencies and reference it in the Dockerfile.

Question 11

Your application runs on Compute Engine and uses Cloud Pub/Sub to receive messages from a third-party service. Recently, the message delivery latency has increased significantly. The third-party reports no issues on their end. You notice that the Pub/Sub subscription's 'ackDeadlineSeconds' is set to 10. What is the most likely cause of the latency?

Accepted Answer

The ackDeadlineSeconds is too short, causing frequent message redelivery.. A is correct because a 10-second ackDeadlineSeconds is very short. If your subscriber cannot process and acknowledge messages within 10 seconds, Pub/Sub will consider them unacknowledged and redeliver them. This redelivery causes duplicate processing and increases overall latency as messages are repeatedly sent back to the subscriber, delaying their final consumption.

Answer

The topic's message retention duration is too long.

Answer

The push endpoint is not responding, causing Pub/Sub to retry.

Answer

The subscription has an exponential backoff policy that is too aggressive.

Question 12

A company is migrating a MySQL database with MyISAM tables to Cloud SQL for MySQL. They want to ensure the target database uses InnoDB for better transactional support and crash recovery. What should they do?

Accepted Answer

Run ALTER TABLE table_name ENGINE=InnoDB on each MyISAM table before migration.. MyISAM tables must be converted to InnoDB before or during migration. The ALTER TABLE statement is the standard way to change the storage engine in MySQL.

Answer

Set the default_storage_engine flag to InnoDB on the source MySQL instance.

Answer

Enable the skip_myisam flag in Cloud SQL to automatically convert MyISAM to InnoDB.

Answer

Use mysqldump with the --compatible=innodb option.

Question 13

A company is designing a globally distributed application using Cloud Spanner. The application requires strong consistency and the ability to handle high read/write throughput. The team is concerned about inter-continental latency. Which two design choices would optimize performance while maintaining strong consistency? (Choose two.)

Accepted Answer

Enable leader-optimized routing to direct reads to the nearest leader region.. A is correct because leader-optimized routing directs read requests to the nearest region that contains the leader replica for the requested data, reducing inter-continental latency while still reading from the leader to ensure strong consistency. C is correct because placing a multi-region Spanner instance in geographic locations close to users minimizes network round-trip time, and Spanner's synchronous replication across regions maintains strong consistency even with high read/write throughput.

Answer

Use read-only replicas in each continent to serve reads locally.

Answer

Implement client-side caching with a short TTL for frequently accessed data.

Answer

Increase the number of nodes in the Spanner instance to improve throughput.

Question 14

Which THREE are valid methods to create custom metrics in Cloud Monitoring?

Accepted Answer

Using the Cloud Monitoring API to write metric points.. The Cloud Monitoring API allows you to write custom metric points directly using the `projects.timeSeries.create` method. This enables you to define your own metric descriptors and send time-series data to Cloud Monitoring, which is a fundamental way to create custom metrics.

Answer

Using Cloud Console's Metrics Explorer to manually enter data.

Answer

Using Cloud Functions to emit metrics via Stackdriver Monitoring API.

Question 15

A team is using Cloud Spanner for a global application. They notice that read latency is high for queries that filter on a non-key column. The table has a primary key of (CustomerID, OrderDate) and there are millions of rows. The query uses a WHERE clause on the 'Status' column. The team wants to reduce latency without significantly increasing storage costs. What is the most effective action?

Accepted Answer

Create a secondary index on the 'Status' column.. Creating a secondary index on the 'Status' column (Option B) allows Cloud Spanner to directly locate rows matching the filter without scanning the entire table. This reduces read latency because Spanner can use the index to perform a point lookup or small range scan instead of a full table scan. Indexes in Spanner are stored as separate tables, but they add minimal storage overhead compared to the latency improvement they provide.

Answer

Create an interleaved table for 'Status' values.

Answer

Increase the number of nodes in the Spanner instance.

Answer

Use stale reads with a 15-second staleness.

Question 16

A global e-commerce application uses Cloud Spanner. Some queries need to read data that is up to 10 seconds stale to reduce latency. How can the application achieve this while minimizing read latency?

Accepted Answer

Use a stale read with a max staleness of 10 seconds. Cloud Spanner supports bounded staleness reads (stale reads) which allow reading data as of a specific timestamp in the past, reducing latency by avoiding strong read barriers. Using a read timestamp 10 seconds in the past achieves this.

Answer

Use a global secondary index

Answer

Use a strong read with a read timestamp

Answer

Use the Mutations API to read data

Question 17

A developer deploys a Cloud Function (2nd gen) that processes messages from Pub/Sub. The function sometimes fails with 'Deadline Exceeded' for messages that take longer than 9 minutes. What should the developer do to handle these long-running messages without losing them?

Accepted Answer

Set the Pub/Sub subscription acknowledgment deadline to 10 minutes and implement a push endpoint that acknowledges after processing.. Cloud Functions (2nd gen) have a maximum timeout of 60 minutes, but Pub/Sub push subscriptions have a default acknowledgment deadline of 10 seconds. By setting the acknowledgment deadline to 10 minutes and implementing a push endpoint that acknowledges after processing, the developer ensures the message is not redelivered prematurely while allowing the function up to 10 minutes to complete. This prevents 'Deadline Exceeded' errors for messages that take longer than 9 minutes without losing messages, as the subscription will wait for the acknowledgment before considering the message as failed.

Answer

Configure the function to retry on failure and set a maximum retry count.

Answer

Increase the Cloud Function timeout to 60 minutes.

Answer

Use Cloud Tasks instead of Pub/Sub for asynchronous invocation.

Question 18

You need to monitor the CPU usage of a Compute Engine instance and trigger an alert when it exceeds 80% for 5 minutes. Which Google Cloud service should you use?

Accepted Answer

Cloud Monitoring. Cloud Monitoring (formerly Stackdriver Monitoring) is the correct service because it provides metrics, dashboards, and alerting policies for Compute Engine instances. You can create a metric-based alert condition that triggers when the CPU utilization metric exceeds 80% for a duration of 5 minutes, using the MQL or policy builder.

Answer

Cloud Debugger

Answer

Cloud Logging

Answer

Error Reporting

Question 19

Drag and drop the steps to set up a Cloud SQL instance with a private IP in the correct order.

Accepted Answer

Create VPC network, Allocate IP range for private services access, Create private services access connection, Create Cloud SQL instance with private IP. Setting up private IP Cloud SQL requires a VPC, private services access, and creating the instance with private IP.

Answer

Create VPC network, Create private services access connection, Allocate IP range for private services access, Create Cloud SQL instance with private IP

Answer

Allocate IP range for private services access, Create VPC network, Create private services access connection, Create Cloud SQL instance with private IP

Answer

Create Cloud SQL instance with private IP, Create VPC network, Allocate IP range for private services access, Create private services access connection

Question 20

A company is running a critical application on Google Kubernetes Engine (GKE) that stores state in a Cloud SQL PostgreSQL instance. The application's latency-sensitive frontend needs to read data from Cloud SQL with minimal latency. The team wants to reduce read latency and offload read traffic from the primary database. What should they do?

Accepted Answer

Create a read replica of the Cloud SQL instance and direct read traffic to the replica.. Creating a read replica of the Cloud SQL PostgreSQL instance allows read-heavy, latency-sensitive traffic to be offloaded from the primary database. The replica handles SELECT queries independently, reducing load on the primary and lowering read latency for the frontend, as replicas are typically in the same region and can serve data with minimal additional delay.

Answer

Migrate the database to Cloud Spanner for better read scalability.

Answer

Use Memorystore for Redis as a cache layer between the application and Cloud SQL.

Answer

Use Cloud CDN to cache database responses.