PCDE Practice Test 12 — 15 Questions

Question 1

An e-commerce site uses Cloud SQL for MySQL. They need read scalability for product catalog queries. What should they do?

Accepted Answer

Add read replicas. Adding read replicas in Cloud SQL for MySQL offloads read traffic from the primary instance, providing horizontal read scalability for product catalog queries. Replicas asynchronously replicate data using MySQL's native binary log replication, allowing the primary to focus on writes while replicas handle read-heavy workloads.

Answer

Partition tables

Answer

Use Cloud Spanner

Answer

Enable automatic storage increase

Question 2

Which THREE are considerations when designing a schema for Cloud Firestore?

Accepted Answer

Use subcollections to organize related data. Subcollections in Cloud Firestore allow you to organize related data hierarchically within a document, enabling efficient queries and scalability without hitting the 1 MiB document size limit. This structure is ideal for data like user posts or product reviews, where each subcollection can grow independently.

Answer

Use nested maps for deeply structured data

Answer

Always use transactional writes to ensure consistency

Question 3

Which TWO actions can help reduce the number of read replicas needed for a Cloud SQL for PostgreSQL instance that serves a read-heavy workload?

Accepted Answer

Implement connection pooling to reuse database connections.. Connection pooling reduces the overhead of establishing new database connections, which can consume significant CPU and memory resources on the primary instance. By reusing existing connections, the primary instance can handle more read requests without needing additional read replicas to offload the connection management load. This directly reduces the number of replicas required for a read-heavy workload.

Answer

Enable synchronous replication on all read replicas.

Answer

Use smaller machine types for read replicas.

Answer

Increase the max_connections parameter on the primary instance.

Question 4

An engineer wants to trigger a Cloud Build pipeline automatically whenever a pull request is created against the main branch of a GitHub repository. Which type of build trigger should they configure?

Accepted Answer

Pull request trigger. Cloud Build supports a dedicated pull request trigger type that fires when a PR is opened, updated, or reopened against a specified branch. Because the requirement is specifically to run on PR creation against main, the pull request trigger is the exact match. It also supports comment control, so builds can require a reviewer's /gcbrun comment before executing.

Answer

Scheduled trigger

Answer

Manual trigger

Answer

Push to branch trigger

Question 5

A team is reviewing IAM permissions on a Cloud Storage bucket. The exhibit shows the bucket's IAM policy. A developer is using the service account sa-1 and reports that they cannot delete objects in the bucket. What is the likely reason?

Accepted Answer

The service account sa-1 does not have the storage.objects.delete permission.. The IAM policy shown in the exhibit grants the `objectViewer` role to service account `sa-1`, which includes the `storage.objects.get` and `storage.objects.list` permissions but does not include `storage.objects.delete`. Without the `storage.objects.delete` permission, the developer cannot delete objects in the bucket, even if they can view them. The correct answer is B because the service account lacks the necessary delete permission.

Answer

The etag value must be updated before any delete operation.

Answer

A condition is attached to the objectViewer role that prevents deletion.

Answer

The policy only allows deletion by the service account sa-2.

Question 6

Which GCP database service automatically replicates data across multiple zones within a region and provides an SLA of 99.999% for multi-region configurations?

Accepted Answer

Cloud Spanner. Cloud Spanner is Google's globally distributed, strongly consistent relational database that automatically replicates across zones within a region and offers a 99.999% SLA for multi-region configurations. Its synchronous replication and TrueTime-based consistency make it the only GCP database with that availability guarantee.

Answer

Firestore

Answer

Cloud SQL

Answer

Cloud Bigtable

Question 7

A company runs a critical application on Cloud SQL for PostgreSQL with a 5-minute RPO and 30-minute RTO. They have a cross-region read replica for disaster recovery. During a planned failover test, what is the expected RPO and RTO when promoting the read replica?

Accepted Answer

RPO = replication lag, RTO = minutes. When promoting a cross-region read replica in Cloud SQL for PostgreSQL, the replica may lag behind the primary, so the RPO equals the replication lag at the time of promotion, and the RTO is typically minutes due to the promotion and DNS/connection reconfiguration steps. This matches the stated 5-minute RPO and 30-minute RTO requirements.

Answer

RPO = 0, RTO = less than 1 minute

Answer

RPO = 0, RTO = minutes

Answer

RPO = backup age, RTO = hours

Question 8

A team wants to automatically adjust the node count in a GKE cluster based on pending pod resource requests. Which component should they enable?

Accepted Answer

Cluster Autoscaler. The Cluster Autoscaler watches for pods that cannot be scheduled due to insufficient resources and adds nodes to the node pool; it also removes underutilized nodes. Since the requirement is to adjust node count based on pending pod resource requests, Cluster Autoscaler is the correct component.

Answer

Vertical Pod Autoscaler

Answer

Node auto-provisioning

Answer

Horizontal Pod Autoscaler

Question 9

A company is migrating Oracle to Cloud SQL for PostgreSQL using Ora2Pg. For a column defined as NUMBER(10,2) in Oracle, what is the corresponding data type in PostgreSQL?

Accepted Answer

NUMERIC(10,2). Oracle's NUMBER(10,2) specifies a fixed-point number with up to 10 digits total and 2 digits after the decimal point. PostgreSQL's NUMERIC(10,2) is the direct equivalent, offering identical precision and scale semantics. Ora2Pg automatically maps NUMBER(p,s) to NUMERIC(p,s) to preserve exact numeric storage.

Answer

INTEGER

Answer

DOUBLE PRECISION

Answer

TEXT

Question 10

A data engineer is creating a reporting layer in BigQuery for BI tools. Which TWO practices improve query performance?

Accepted Answer

Use approximate aggregate functions when exact accuracy is not needed.. BigQuery's approximate aggregate functions (e.g., APPROX_COUNT_DISTINCT, APPROX_QUANTILES) use HyperLogLog++ and other sketching algorithms to return results with a small, bounded error (typically <1%) while drastically reducing the amount of data scanned and shuffled. This trade-off is ideal for BI dashboards where exact counts are not critical, as it can cut query execution time by orders of magnitude.

Answer

Use SELECT * in queries.

Answer

Use ORDER BY in subqueries unnecessarily.

Answer

Store all data in a single table without partitioning.

Question 11

An SRE team wants to define an SLI for service availability. Which metric correctly represents the availability SLI?

Accepted Answer

Total requests that succeed / Total requests. Availability as an SLI is measured as the proportion of successful requests to total requests. Option A correctly defines this as 'Total requests that succeed / Total requests'. Option B is incorrect because it measures latency (response time within 200 ms), not availability. Option C is a measure of uptime, not service availability from the user's perspective. Option D only counts errors, which is not a ratio.

Answer

Total requests that complete within 200 ms / Total requests

Answer

Total minutes the service is up / Total minutes in the window

Answer

Number of requests that return a 5xx status code

Question 12

Your company runs a global application on Cloud Spanner. You notice that recent schema changes have caused a significant increase in latency for cross-node transactions. The previous schema used interleaved tables for parent-child relationships, but the new schema uses separate tables with foreign keys. What is the most likely cause of the increased latency?

Accepted Answer

The new schema uses foreign keys that require cross-node transactions.. The new schema uses separate tables with foreign keys instead of interleaved tables. In Cloud Spanner, interleaved tables guarantee that parent and child rows are co-located on the same split, allowing local joins without cross-node communication. Foreign keys between non-interleaved tables can reference rows stored on different splits, forcing distributed transactions that require two-phase commit across nodes, which significantly increases latency.

Answer

The new schema does not use commit timestamps for versioning.

Answer

The new schema lacks secondary indexes on foreign key columns.

Answer

The Spanner instance was not resized after the schema change.

Question 13

A team uses Terraform with a GCS backend. After a failed apply, the state file is corrupted. How can they recover to the last known good state?

Accepted Answer

Restore a previous version of the state file from GCS object versioning. GCS object versioning retains prior generations of the state object, so restoring the last known good generation recovers a consistent state file without manual reconstruction. This is the standard Terraform recovery pattern for a corrupted remote state, since the backend simply reads whatever object is current. After restoring, run 'terraform plan' to verify the state matches real infrastructure before any further apply.

Answer

Use 'terraform force-unlock' to release the lock and then 'terraform apply' again

Answer

Run 'terraform state rm' to remove corrupted resources and re-import

Answer

Manually edit the state file in GCS using the JSON editor

Question 14

An engineering team wants to automatically build a Docker image every time a developer pushes code to the main branch of their GitHub repository. They are using Cloud Build. Which configuration should they use?

Accepted Answer

Cloud Build trigger with push event and branch pattern 'main'. A Cloud Build trigger with a push event and branch pattern 'main' will automatically start a build when code is pushed to the main branch. This matches the requirement to build a Docker image on every push to main. The trigger can be configured to use a cloudbuild.yaml file that defines the build steps, including building and pushing the Docker image.

Answer

Cloud Build trigger with manual invocation

Answer

Cloud Build trigger with scheduled event

Answer

Cloud Build trigger with pull request event

Question 15

Your Firestore database in Native mode is used by a mobile app. You need to query a collection where documents are filtered by two fields: 'status' (string) and 'createdAt' (timestamp). The query is not performing as expected. What action is required?

Accepted Answer

Create a composite index on the 'status' and 'createdAt' fields.. Firestore in Native mode requires a composite index to efficiently query documents filtered by multiple fields, such as 'status' and 'createdAt'. Without this index, the query may fail or perform poorly, as Firestore cannot combine separate single-field indexes for equality and range filters. Option C is correct because creating a composite index on both fields enables the query to run as expected.

Answer

Create an index exemption for the collection to allow multi-field queries.

Answer

Add a third field to the query to make it more specific.

Answer

Ensure that single-field indexes exist for both 'status' and 'createdAt'.