PDE Practice Exam 3 — 20 Questions

Question 1

A data engineer is preparing a dataset for ML training in Vertex AI. The dataset includes a timestamp column, a categorical column with high cardinality (1000 distinct values), and a numerical column with outliers. Which two preprocessing steps should they apply? (Choose TWO)

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

Accepted Answer

Label encode the categorical column. One-hot encoding for high cardinality may be too sparse; label encoding (ordinal encoder) is more common. Winsorizing clips outliers.

Answer

Drop the timestamp column

Answer

Normalize the numerical column using Z-score

Answer

One-hot encode the categorical column

Question 2

A company runs a Dataflow pipeline that reads from Pub/Sub, aggregates events in a 10-minute fixed window, and writes to BigQuery. Recently, the pipeline has been failing with 'high uncommitted bytes' errors during periods of high traffic. What is the most likely cause and recommended action?

Accepted Answer

Use a global window with a trigger that fires early based on element count to reduce the number of open windows.. The 'high uncommitted bytes' error in Dataflow occurs when the system holds too much data in memory across many open windows, exceeding the default 200 MB limit. Using a global window with an early trigger based on element count reduces the number of simultaneous open windows and allows data to be committed more frequently, preventing memory pressure. This approach is recommended over reducing window size or scaling workers because the root cause is window fan-out, not throughput or parallelism.

Answer

Reduce the window size from 10 minutes to 1 minute to decrease the amount of data per window.

Answer

Increase the number of worker machines to handle higher throughput.

Answer

Set a maximum number of workers and use a Pub/Sub flow control setting to limit incoming messages.

Question 3

Refer to the exhibit. A team is trying to run a custom prediction container on Vertex AI Endpoint. They get this error when the container starts. What is the most likely cause?

Accepted Answer

The entry point is missing or incorrect. The error occurs when the container starts, which typically happens during the initial health check or readiness probe. Vertex AI Endpoints require a valid entry point (e.g., CMD or ENTRYPOINT in the Dockerfile) to start the prediction server. If the entry point is missing or incorrect, the container fails to launch, resulting in the observed error.

Answer

The container image is too large

Answer

The container is built for a different CPU architecture

Answer

The model file is missing from the container

Question 4

A data engineer is building a Cloud Workflows workflow that orchestrates multiple Cloud Functions and API calls. The workflow should handle transient failures with retries and send a notification to a Pub/Sub topic if the workflow ultimately fails. Which THREE steps should the engineer include in the workflow definition?

Accepted Answer

Use the 'googleapis.pubsub.v1.projects.topics.publish' connector to send a failure notification.. Workflows supports retry policies via 'retry' blocks, conditional steps using 'switch', and Pub/Sub publishing via the 'googleapis.pubsub.v1.projects.topics.publish' connector. The 'try/catch' is not a Workflows construct; instead, use 'step' with 'retry' and 'on_error' for failure handling. 'for' loops are for iteration, not error handling.

Answer

Use a 'for' loop to iterate over retries.

Answer

Use a 'try' / 'catch' block to handle exceptions and route to a failure step.

Question 5

A company uses Cloud Composer (Airflow) to orchestrate pipelines. They want to implement a pattern where a task polls for a file arrival in Cloud Storage and then triggers subsequent tasks. Which THREE Airflow concepts are essential? (Choose 3)

Accepted Answer

Sensors (e.g., GCSObjectExistenceSensor). A is correct because Sensors are a specialized type of operator designed to wait for a specific condition, such as file arrival in Cloud Storage. The `GCSObjectExistenceSensor` in Cloud Composer (Airflow) polls Google Cloud Storage at a configurable interval until the target file exists, making it the precise tool for this file-arrival polling pattern.

Answer

Operators (e.g., PythonOperator)

Answer

SubDAGs for grouping tasks

Question 6

Your company uses Vertex AI Pipelines to automate model retraining. The pipeline has three steps: data extraction from BigQuery, feature engineering using Dataflow, and model training using a custom container on Vertex AI Training. Recently, the pipeline has been failing intermittently at the Dataflow step with a 'The job encountered a transient error. Please retry.' message. You have enabled pipeline retries with 3 attempts. However, the pipeline still fails after 3 retries. You check the logs and find that the Dataflow job requires more resources than the default worker configuration provides. Which change should you make to reduce the failure rate?

Accepted Answer

Increase the Dataflow worker machine type to have more memory and CPU in the pipeline step configuration. The pipeline fails due to insufficient resources (memory and CPU) in the default Dataflow worker configuration. By increasing the worker machine type (e.g., using a custom machine type with more vCPUs and memory), the Dataflow job can handle the feature engineering workload without hitting resource limits, reducing transient failures. This directly addresses the root cause identified in the logs, unlike retries or parallelism changes.

Answer

Increase the number of Dataflow workers to improve parallelism

Answer

Increase the number of retries in the pipeline to 5

Answer

Replace Dataflow with Dataproc to run the feature engineering step

Question 7

A production model deployed on Vertex AI Endpoint is experiencing high latency during traffic spikes. The current configuration uses a single replica. What is the most efficient solution?

Accepted Answer

Enable autoscaling with minReplicaCount=1 and maxReplicaCount=10. Enabling autoscaling with minReplicaCount=1 and maxReplicaCount=10 allows Vertex AI Endpoint to dynamically add replicas during traffic spikes, distributing inference requests across multiple instances and reducing latency. This is the most efficient solution as it scales resources up only when needed, avoiding over-provisioning and minimizing cost during low traffic periods.

Answer

Set a higher min replica count (e.g., 3)

Answer

Use a larger machine type (e.g., n1-highmem-8)

Answer

Switch to batch prediction to handle spikes

Question 8

Which THREE of the following are best practices when designing a Cloud Dataflow pipeline for batch processing? (Choose three.)

Accepted Answer

Use side inputs to hold a large lookup table that is read in every element.. Side inputs in Cloud Dataflow are designed to efficiently broadcast a read-only dataset (like a lookup table) to all parallel workers. When the side input is a large but static dataset, Dataflow can cache it in memory or on disk across workers, avoiding repeated external lookups and reducing per-element processing overhead. This pattern is especially effective for batch processing where the side input is read once and reused across all elements.

Answer

Use mutable state within ParDo to track running totals.

Answer

Always insert a Reshuffle transform after every GroupByKey to redistribute data.

Question 9

Which TWO best practices should be followed when managing multiple model versions on Vertex AI Endpoints for a production system?

Accepted Answer

Use traffic splitting to gradually shift traffic to a new version while monitoring performance.. Vertex AI Endpoints support traffic splitting, allowing you to route a percentage of inference requests to a new model version while the rest goes to the existing version. This enables gradual rollout, monitoring of performance metrics (e.g., latency, error rate), and safe rollback without downtime. It is a best practice for production systems to validate a new version before fully cutting over.

Answer

Always keep all historical versions deployed to enable fast rollback.

Answer

If two versions share the same endpoint, they must have exactly the same machine type.

Answer

Use the same endpoint for multiple versions and adjust min_replica_count, max_replica_count for each version.

Question 10

A data engineer needs to automatically delete objects from a Cloud Storage bucket after 30 days and archive them to nearline storage after 7 days. Which configuration should they use?

Accepted Answer

Set a lifecycle rule to SetStorageClass to nearline after 7 days and delete after 30 days. It implements a lifecycle rule that first transitions objects to Nearline storage after 7 days (reducing costs for infrequently accessed data) and then deletes them after 30 days. This matches the requirement to archive after 7 days and delete after 30 days, using the `SetStorageClass` and `Delete` actions in the correct chronological order.

Answer

Set a lifecycle rule to SetStorageClass to nearline after 30 days only

Answer

Set a lifecycle rule to delete objects after 7 days only

Answer

Set a lifecycle rule to delete objects after 7 days and SetStorageClass to nearline after 30 days

Question 11

You are a data engineer at a financial services company that uses Vertex AI to train and deploy models for credit risk assessment. The company has strict governance requirements: every model version must be approved by the risk committee before going to production. The approval process can take several days. Currently, the team trains a new model weekly and manually deploys it to a staging endpoint for review, then manually promotes to production after approval. This process is error-prone and slow. You want to automate the pipeline: training should trigger automatically when new data arrives, the model should be automatically deployed to a staging endpoint for review, and after manual approval, it should be promoted to production. Additionally, you need to ensure that if a model in staging performs poorly (e.g., low accuracy), it should not be promoted even if approved. What should you do?

Accepted Answer

Create a Vertex AI Pipeline that: (1) Triggers on new data, (2) Trains model, (3) Evaluates and stores metrics in the model registry, (4) Deploys to staging endpoint as a new model version. Then use a manual approval step (e.g., via Cloud Build approval or external system) to trigger a second pipeline that checks the stored metrics and, if acceptable, deploys to production endpoint.. The best approach uses Vertex AI Pipelines to automatically train and deploy to a staging endpoint. After manual approval, a separate pipeline step checks model performance metrics (which were stored during training/evaluation) and if they meet a threshold, promotes to production. This enforces governance and automation.

Answer

Use Vertex AI Experiments to track model versions, then manually deploy from the Experiments UI.

Answer

Use Cloud Scheduler to run training weekly, then use Cloud Functions to deploy to staging, and after manual approval, use another Cloud Function to check performance and deploy to production.

Answer

Train models on Vertex AI Workbench and use a CI/CD tool like Cloud Build to deploy to staging. Use a Cloud Build approval step to promote to production after manual check.

Question 12

A company wants to analyze server logs stored in Cloud Storage using SQL. They need to get results in seconds without setting up any clusters. Which service should they use?

Accepted Answer

BigQuery. BigQuery is a serverless, highly scalable, and cost-effective multi-cloud data warehouse designed for business agility. It allows you to analyze petabytes of data using standard SQL without needing to provision or manage any clusters, making it ideal for querying server logs stored in Cloud Storage directly via external tables or loading data into BigQuery for sub-second query performance.

Answer

Cloud Dataflow

Answer

Cloud Logging

Answer

Cloud Dataproc

Question 13

A data science team wants to deploy a model that requires a custom container with specific NVIDIA CUDA version. They build the image and push to Artifact Registry. When deploying to Vertex AI, the model fails to load with an error: 'Failed to start container: invalid ELF header'. What is the most likely cause?

Accepted Answer

The container image was built for a different CPU architecture (e.g., ARM64) than the Vertex AI machine (x86_64). The image was built for the wrong architecture (e.g., building on an ARM Mac for a x86 deployment). Option B (CUDA version mismatch) would cause a different error. Option C (container permissions) would cause a permission denied error. Option D (model file format) would cause loading errors but not container startup failure.

Answer

The model file (saved as .pkl) is corrupted

Answer

The CUDA version in the container is incompatible with the GPU on the machine

Answer

The container does not have the necessary permissions to access the model file in Cloud Storage

Question 14

A data engineer needs to move 500 TB of archival data from an on-premises Hadoop cluster to Cloud Storage. The network bandwidth is limited to 100 Mbps, and the transfer must complete within 30 days. Which method is most cost-effective and reliable?

Accepted Answer

Use Transfer Appliance to ship the data offline. With 100 Mbps, transferring 500 TB over the network would take > 500 days, exceeding the 30-day window. Transfer Appliance is designed for petabyte-scale offline transfers, making it the only feasible option.

Answer

Use Dataproc to copy data in parallel

Answer

Use a VPN and gsutil rsync

Answer

Use Storage Transfer Service over the internet

Question 15

You are designing a data pipeline that ingests streaming data from Pub/Sub, processes it with Dataflow, and writes to BigQuery. You need to ensure that schema changes in the incoming data (new fields) are handled without pipeline failure. Which THREE steps should you take? (Choose THREE.)

Accepted Answer

Set the BigQuery table schema to allow automatic addition of new fields by using 'ignore_unknown_values'.. To handle schema drift, BigQuery allows schema relaxation (adding nullable columns) via DDL. Dataflow can update the destination table schema using BigQuery APIs (e.g., set the schema to include unknown fields). Alternatively, using BigQuery's automatic schema detection with 'ignore_unknown_values' can allow new fields to be added automatically. Setting all fields to NULLABLE in advance is not practical. Setting the table to require all fields causes failures on unknown fields.

Answer

Configure the BigQuery table to require all fields, causing the pipeline to fail on unknown fields.

Answer

Set all columns in the BigQuery table as NULLABLE from the start.

Question 16

A company uses BigQuery flat-rate pricing with 500 slots purchased as a committed use discount. During peak hours, they need additional capacity but do not want to buy more committed slots. They have a secondary project used for ad-hoc queries by analysts. How can they provide burst capacity to the primary project during peak times without increasing committed spend?

Accepted Answer

Create flex slots in the secondary project, create a reservation in the secondary project, and assign the reservation to the primary project.. Flex slots provide temporary capacity without long-term commitment. By creating flex slots in a secondary project and assigning the reservation to the primary project, burst capacity is added during peak times without increasing committed spend. Option B is incorrect because autoscaling can be used with committed use reservations, but it does not provide capacity beyond the purchased slots without incurring additional costs; autoscaling on committed use still uses flex pricing. Option C is incorrect because upgrading to Enterprise Plus does not inherently provide burst capacity without additional slots. Option D is incorrect because purchasing additional committed use slots increases committed spend.

Answer

Enable autoscaling slot management in the primary project's reservation, allowing slots to scale up based on demand.

Answer

Upgrade the primary project's edition to Enterprise Plus to allow bursting.

Answer

Purchase additional committed use slots in the primary project and apply them to the reservation.

Question 17

Your company is building a data processing system that ingests sensor data from millions of devices, processes it in near real-time to detect anomalies, and stores raw and processed data for long-term analytics. The system must meet a 99.9% uptime SLA and minimize data loss. Which THREE design choices are best? (Choose three.)

Accepted Answer

Use Cloud Pub/Sub as the ingestion layer with a dead-letter topic to capture unprocessed messages.. Cloud Pub/Sub with a dead-letter topic ensures that messages that cannot be processed are captured and not lost, directly supporting the requirement to minimize data loss. The dead-letter topic allows for later reprocessing or analysis of failed messages, which is critical for meeting a 99.9% uptime SLA by preventing message backlogs from blocking the ingestion pipeline.

Answer

Store raw data in Cloud Bigtable and processed data in Cloud Storage.

Answer

Use a global Cloud Load Balancer in front of the Dataflow workers.

Question 18

Which TWO options can help reduce costs for a Dataflow batch pipeline that processes 100 GB of data daily from Cloud Storage? (Choose 2)

Accepted Answer

Use FlexRS (Flexible Resource Scheduling). FlexRS (Flexible Resource Scheduling) allows you to run batch workloads on a discounted, flexible schedule. It reduces costs by offering lower prices in exchange for the job being able to wait up to 6 hours for resources to become available. This is ideal for a daily 100 GB batch pipeline that can tolerate some scheduling delay.

Answer

Use Dataflow Prime (now Dataflow Runner v2)

Answer

Use high-memory machine types

Answer

Use Streaming Engine

Question 19

Match each data encryption concept to its description.

Accepted Answer

Customer-Managed Encryption Keys (CMEK): You manage key material in Cloud KMS and use it to protect data.. The correct matches are: CMEK involves managing keys in Cloud KMS; CSEK involves supplying your own keys; default encryption uses Google-managed keys; encryption in transit uses TLS. Common confusions include swapping CMEK and CSEK.

Answer

Customer-Managed Encryption Keys (CMEK): You supply your own encryption keys.

Answer

Default Encryption at Rest: You manage keys in Cloud KMS.

Question 20

A company uses Cloud Build to deploy containerized applications. They want to ensure build and deployment quality. Which THREE steps should they include in their CI/CD pipeline? (Choose three.)

Accepted Answer

Scan container images for vulnerabilities using Container Analysis.. Container Analysis (now part of Artifact Registry) scans container images for known vulnerabilities (CVEs) in OS packages and application dependencies. Integrating this scan into the CI/CD pipeline ensures that only compliant images proceed to deployment, preventing vulnerable code from reaching production. This directly supports the 'Ensuring solution quality' domain by enforcing security gates before release.

Answer

Run unit tests after deployment.

Answer

Deploy directly to production on every commit.