PCDE Mock Exam 71 — 25 Questions

Question 1

Your GKE cluster is running a critical web application that experiences predictable traffic spikes during business hours. You want to minimize latency and avoid pod startup delays during scaling. The application uses CPU-intensive image processing. Which scaling strategy should you use?

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

Accepted Answer

Configure HPA with a minimum of 2 replicas and scale on CPU utilization; enable cluster autoscaler for node provisioning.. To avoid cold starts while ensuring pods can handle CPU spikes, you need a baseline of pods and dynamic scaling responsive to CPU. HPA with a minimum replicas of 2 ensures baseline capacity; HPA scales on CPU. Cluster autoscaler adds nodes if needed, but does not directly address pod startup delay. VPA adjusts resource requests, which can help but does not prevent cold starts. Using HPA alone with min replicas avoids pod creation latency.

Answer

Set a high number of static pods equal to peak traffic; use cluster autoscaler to add nodes.

Answer

Use VPA with updateMode: Auto to automatically adjust pod resources; enable cluster autoscaler to add nodes as required.

Answer

Deploy a CronJob to scale up replicas before business hours; rely on HPA to handle the rest.

Question 2

A Looker developer configured a new connection to BigQuery as shown. The connection test fails with the error above. What is the most likely cause?

Accepted Answer

The Looker service account lacks the required BigQuery roles on the dataset. The error indicates a permissions issue during the connection test. Looker uses a service account to authenticate to BigQuery, and if that service account lacks the required BigQuery roles (e.g., BigQuery Data Viewer, BigQuery Job User) on the dataset, the connection test will fail with an access denied error. The error message shown in the question (not provided here but implied) typically states 'Access Denied' or 'Permission denied' when the service account does not have the necessary IAM permissions on the dataset or project.

Answer

The dataset mydataset does not exist in the project

Answer

The BigQuery query quota has been exceeded for the project

Answer

The Looker instance is located in a different region than the BigQuery dataset

Question 3

In Cloud Bigtable, a table has a high ratio of garbage collection (GC) that causes performance degradation during compaction. What is the best practice to monitor and optimize this?

Accepted Answer

Use Cloud Monitoring to track garbage collection count and adjust GC settings. Cloud Monitoring provides the metrics (e.g., 'bigtable.googleapis.com/table/garbage_collection_count') needed to track GC activity, and adjusting GC settings (e.g., column family max versions or TTL) directly reduces the compaction overhead caused by excessive stale data. This aligns with best practices for proactive performance optimization in Cloud Bigtable.

Answer

Use the bigtableadmin API to view table stats

Answer

Compact the table manually

Answer

Increase node count

Question 4

A company is migrating a legacy on-premises MySQL database to Cloud SQL for PostgreSQL. The database uses composite primary keys on multiple tables and heavily relies on cross-table joins with foreign keys. The team wants to minimize application code changes during migration. Which schema design strategy should the Cloud Database Engineer recommend to ensure compatibility and performance?

Accepted Answer

Use the same composite primary keys and foreign key constraints in Cloud SQL for PostgreSQL, leveraging its full support for these features.. Cloud SQL for PostgreSQL fully supports composite primary keys and foreign key constraints, which are standard SQL features. By maintaining the same schema, the team minimizes application code changes while preserving referential integrity and join performance, as PostgreSQL's query planner handles these constructs efficiently.

Answer

Maintain the same schema and rewrite joins as materialized views in PostgreSQL to optimize queries.

Answer

Migrate to Cloud Spanner instead, using interleaved tables to replace join-heavy operations.

Answer

Remove composite primary keys and replace them with surrogate keys; use look-up tables for foreign key relationships.

Question 5

A company is designing a BigQuery data warehouse for BI dashboards. They have a fact table with billions of rows and need to optimize query performance for common filters on date and customer_id. Which table design strategy is most effective?

Accepted Answer

Use a partitioned table on date with clustering on customer_id.. Partitioning the table on `date` allows BigQuery to prune entire partitions when filtering by date, drastically reducing the data scanned. Clustering on `customer_id` then sorts data within each partition, enabling block-level pruning for queries that filter on `customer_id`. This combination minimizes both I/O and cost for the described BI workload.

Answer

Use a clustered table on date only.

Answer

Use a non-partitioned table with indexing on customer_id.

Answer

Use a materialized view that aggregates by date.

Question 6

A company wants to create a BI dashboard that shows daily active users. The data is stored in a BigQuery table with columns: user_id, activity_date, and event_type. Which two optimizations would help reduce query costs? (Choose two.)

Accepted Answer

Use a materialized view with COUNT(DISTINCT user_id) grouped by activity_date.. A materialized view precomputes the COUNT(DISTINCT user_id) grouped by activity_date, so queries against it read only the pre-aggregated results rather than scanning the entire base table. This drastically reduces the amount of data processed, lowering query costs in BigQuery's on-demand pricing model where cost is proportional to bytes processed.

Answer

Cluster the table by event_type.

Answer

Use SELECT * and filter in the BI tool.

Answer

Avoid using the LIMIT clause.

Question 7

An organization wants to enforce that no Compute Engine instances have external IP addresses except for a specific project. Which TWO steps should they take? (Choose 2)

Accepted Answer

In the exception project, override the policy to allow.. Set an organization policy to disable external IP at the organization level, then create a policy exception for the allowed project. Alternatively, use a constraint with an exception.

Answer

Add a firewall rule to block traffic to external IPs.

Answer

Remove the external IP from all instances manually.

Answer

Use VPC Service Controls to restrict external access.

Question 8

You have a Memorystore for Redis instance used as a cache. You need to scale it to handle increased load. The current instance is Basic Tier with 2 GB memory. Which TWO actions can you take to scale the instance? (Choose two.)

Accepted Answer

Vertically scale the instance by increasing its memory size or changing to a higher-tier (e.g., Standard Tier).. Memorystore supports vertical scaling by increasing memory size or changing to a higher tier (e.g., Basic to Standard, or Standard to Standard with more memory) – this is option A. Horizontal scaling is achieved by enabling Redis Cluster, which automatically shards data across multiple nodes – this is option E. Option B (creating additional instances with client-side sharding) is not a supported scaling method for Memorystore because it requires manual management and is not integrated with the service. Option C (changing eviction policy to noeviction) does not scale the instance and risks data loss when memory is full. Option D (adding read replicas) is available only in Standard Tier, but it offloads read traffic, not scales the cache capacity.

Answer

Create additional instances and implement client-side sharding.

Answer

Change the eviction policy to noeviction to allow more data.

Answer

Add read replicas to offload read traffic.

Question 9

A company is using mysqldump to migrate a MySQL database to Cloud SQL. The source database uses InnoDB tables and is running a production workload. They want to ensure a consistent snapshot without locking tables. Which mysqldump flags should they use?

Accepted Answer

--single-transaction --skip-lock-tables. --single-transaction uses a transaction to get a consistent snapshot without locking tables (works with InnoDB). --skip-lock-tables prevents explicit table locks. --lock-all-tables would lock tables. --master-data is for binary log coordinates but not required for consistency.

Answer

--single-transaction --master-data

Answer

--lock-all-tables --flush-logs

Answer

--skip-lock-tables --all-databases

Question 10

Which TWO actions should be taken to enable layer caching for Docker builds using Kaniko in Cloud Build? (Choose two.)

Accepted Answer

Add `--cache-repo` specifying an Artifact Registry repository. Kaniko requires the `--cache-repo` flag to specify an Artifact Registry repository where cached layers will be stored and retrieved. This enables layer caching across builds, reducing build time by reusing unchanged layers. Without this flag, Kaniko does not know where to push or pull cached layers from.

Answer

Use the `docker` builder instead of Kaniko

Answer

Set the `CACHE_LAYERS` substitution variable

Answer

Enable Cloud Build's built-in caching by adding `cache: true`

Question 11

A company has a Firestore database in Native mode. They need to run a query that filters on two fields (status and date) and orders by date. The query is slow and returns an error that a matching index is missing. What must the engineer do to resolve this?

Accepted Answer

Create a composite index on status and date in the Firebase Console or using gcloud.. Firestore requires a composite index on both the equality filter field (status) and the order field (date) when a query uses equality filters on one field and an order on another. Without this composite index, the query cannot be executed efficiently and returns an error. Creating the composite index via the Firebase Console or gcloud CLI resolves the issue.

Answer

Enable single-field indexes for both fields; Firestore will automatically use them.

Answer

Rewrite the query using 'IN' clauses to avoid the need for a composite index.

Answer

Change the database to Datastore mode, which does not require indexes.

Question 12

A team wants to implement GitOps for their Terraform infrastructure. They want to automatically apply changes when a pull request is merged to the main branch. Which approach should they use?

Accepted Answer

Use Cloud Build with a trigger on push to main branch to run `terraform apply`. GitOps involves using a tool like Cloud Build with a trigger that runs Terraform on merge to main. Cloud Build can execute Terraform commands and apply changes.

Answer

Use Cloud Source Repositories with a webhook to a Compute Engine instance that runs Terraform

Answer

Set up a cron job that runs `terraform apply` every hour

Answer

Use Terraform Cloud with VCS integration

Question 13

A Cloud SQL for MySQL instance is experiencing high CPU utilisation (>80%) and slow query performance. The instance has auto-storage increase enabled. Which step should the engineer take to immediately reduce CPU load?

Accepted Answer

Increase the instance tier to a larger machine type. High CPU utilisation is often due to insufficient compute capacity. Increasing the instance tier (vertical scaling) provides more CPU and memory, reducing load. Enabling auto-storage increase only adds disk space, not compute. Creating a read replica distributes read traffic but does not help with CPU load on the primary for write-heavy workloads. Adjusting max_connections may help marginally but is not as effective as increasing compute capacity.

Answer

Reduce the max_connections parameter

Answer

Create a cross-region read replica to offload reads

Answer

Enable auto-storage increase if not already enabled

Question 14

A company wants to implement a service mesh with fault injection for HTTP services running on Google Kubernetes Engine. They need to inject artificial delays and errors into requests to test resilience. Which GCP service should they use?

Accepted Answer

Traffic Director. Traffic Director is a managed traffic control plane that supports HTTP fault injection via the HTTP fault filter. It integrates with GKE ingress.

Answer

Cloud Armor

Answer

Cloud Load Balancing

Answer

Cloud Endpoints

Question 15

A company is running a financial application on Cloud Spanner and needs to ensure strong transactional consistency across regions. The application requires both high write throughput (2000 mutations/second) and read throughput (2000 reads/second). According to Spanner capacity planning, how many processing units (PUs) are needed for the combined workload?

Accepted Answer

1 processing unit (PU). Spanner capacity: write throughput 2000 mutations/second per PU, read throughput 2000 reads/second per PU. For 2000 writes/s and 2000 reads/s, you need 1 PU for writes and 1 PU for reads, but the reads and writes share the same PU. Actually, the formula is: PUs needed = max(write_throughput/2000, read_throughput/2000). For 2000 each, that's max(1,1)=1 PU. However, the question states 'high write throughput (2000 mutations/second) and read throughput (2000 reads/second)'. So 1 PU is sufficient. But note: in practice, you might need more for other factors. The question tests the calculation. The answer is 1 PU.

Answer

2 processing units (PUs)

Answer

4 processing units (PUs)

Answer

0.5 processing units (PUs)

Question 16

A DevOps engineer wants to implement a GitOps workflow for a GKE cluster using a tool that automatically syncs the cluster state with a Git repository. Which Google Cloud service is designed for this purpose?

Accepted Answer

Config Sync. Config Sync is the Google Cloud service specifically designed to implement a GitOps workflow for GKE clusters. It automatically synchronizes the cluster's desired state (as defined in a Git repository) with the actual cluster state, ensuring continuous reconciliation without manual intervention.

Answer

Cloud Run

Answer

Config Connector

Answer

Cloud Deploy

Question 17

A company needs to track costs across different teams and projects. They want to see detailed breakdowns by team, environment, and application. Which GCP feature should they use to tag resources for cost analysis?

Accepted Answer

Resource labels. Labels are key-value pairs that can be attached to resources for cost allocation and reporting. Tags are also available but are used for networking and IAM, not primarily for cost tracking. Billing budgets and export are complementary but not for tagging.

Answer

Billing budgets

Answer

Network tags

Answer

Billing export to BigQuery

Question 18

A Cloud Spanner database contains the Orders table as defined above. The query `SELECT * FROM Orders WHERE CustomerID=123` takes a long time. What is the most likely reason?

Accepted Answer

The table needs a secondary index on CustomerID.. The query `SELECT * FROM Orders WHERE CustomerID=123` filters on the `CustomerID` column, but the primary key of the Orders table is likely defined on a different column (e.g., `OrderID`). Without a secondary index on `CustomerID`, Cloud Spanner must perform a full table scan to find matching rows, which is slow for large tables. Creating a secondary index on `CustomerID` allows Cloud Spanner to directly locate the relevant splits and rows, dramatically reducing latency.

Answer

The ORDER BY clause is missing.

Answer

Interleaving causes extra I/O.

Answer

The primary key is not optimized for this query.

Question 19

A financial services company uses Cloud Spanner with a database that has multiple tables with interleaved relationships. They need to enforce a strict consistency requirement across two related tables that are not interleaved. Which method ensures global strong consistency?

Accepted Answer

Use Spanner's built-in atomicity by executing the updates in a single read-write transaction.. Cloud Spanner provides external consistency (global strong consistency) across all tables, interleaved or not, through the use of distributed read-write transactions that leverage the TrueTime API. By executing updates to both non-interleaved tables within a single read-write transaction, Spanner ensures that all mutations are applied atomically and are visible globally at a single timestamp, meeting the strict consistency requirement.

Answer

Use Cloud Pub/Sub to eventually synchronize the tables.

Answer

Use a commit timestamp-based approach to synchronize writes.

Answer

Use a client-side distributed transaction across the two tables.

Question 20

During a DMS continuous migration from MySQL to Cloud SQL, the full dump phase completed successfully, but the CDC phase is failing with 'Error: binary log not found' after a few minutes. The source MySQL has binary logs enabled. What is the most likely cause?

Accepted Answer

The binary logs were purged due to a short binlog_expire_logs_seconds setting.. DMS requires that binary logs are retained until the CDC phase has consumed them. If logs expire due to a short binlog retention period (e.g., default 1 day), the migration fails. The source should have binlog retention set to 7 days or more.

Answer

The DMS connection profile has incorrect SSL settings.

Answer

The source database was restarted and binary logs were reset.

Answer

The source MySQL server has run out of disk space.