PCD Practice Test 14 — 15 Questions

Question 1

A financial application requires ACID transactions across multiple rows and tables in a single region with less than 10ms latency and strong consistency. The application must handle up to 10,000 transactions per second. Which database should you use?

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

Accepted Answer

Cloud Spanner. Cloud Spanner provides ACID transactions, strong consistency, and horizontal scalability, with latency in the single-digit milliseconds for regional instances. It can handle 10K TPS easily. Cloud SQL is ACID but limited in scaling (read replicas, but not horizontal write scaling). Firestore is NoSQL with limited transaction scope. Bigtable is not ACID.

Answer

Cloud SQL

Answer

Firestore

Answer

Bigtable

Question 2

An engineer needs to create a Cloud SQL MySQL instance that can automatically failover to a standby in a different zone within the same region. Which configuration should be used?

Accepted Answer

Regional HA configuration. Cloud SQL HA configuration creates a primary and a standby instance in different zones within the same region. The standby is synchronously replicated and automatic failover occurs in under 60 seconds. Cross-region failover is not supported; read replicas are for read scaling and DR, not automatic failover. Zonal availability is a single-zone instance without HA.

Answer

Read replica in same zone

Answer

Zonal availability configuration

Answer

Cross-region failover replica

Question 3

A company is migrating an on-premises Oracle database to AlloyDB for PostgreSQL. They need to minimize downtime and ensure data consistency. They plan to use Database Migration Service (DMS). Which migration job type and configuration should they use?

Accepted Answer

Use a continuous migration job that performs an initial full dump followed by CDC replication.. Database Migration Service (DMS) continuous migration jobs perform an initial full dump to establish a baseline, then use Change Data Capture (CDC) to replicate ongoing changes from the source Oracle database to AlloyDB for PostgreSQL. This approach minimizes downtime by allowing the target to stay synchronized with the source until a cutover, ensuring data consistency without requiring a separate manual import step.

Answer

Use a continuous migration job with CDC only, skipping the initial dump.

Answer

Use a batch migration job that exports Oracle data to CSV files and loads them into AlloyDB.

Answer

Use a one-time full dump migration job and then manually import the dump into AlloyDB.

Question 4

You are using Cloud Bigtable to store time-series financial market data. To ensure high availability across zones, you configure cluster replication. What is the recommended replication topology for automatic failover?

Accepted Answer

Two clusters in different zones with replication enabled and multi-cluster routing. Cloud Bigtable achieves automatic failover through multi-cluster routing, which requires at least two clusters in different zones (or regions) with replication enabled. When clusters are in separate zones and multi-cluster routing is configured, the client library automatically redirects traffic to a healthy cluster if one becomes unavailable, providing seamless failover without application changes.

Answer

Two clusters in the same zone

Answer

Single cluster with multi-node configuration

Answer

Three clusters in three regions

Question 5

A global e-commerce platform uses Cloud Spanner. They need to design a schema for product inventory that supports high write throughput and avoids hotspots. Which TWO practices should they follow? (Select 2 answers)

Accepted Answer

Use a composite primary key with a hash prefix. Option C is correct because Cloud Spanner hotspots occur when sequential keys concentrate writes on a single split; adding a hash prefix to a composite primary key (e.g., hashing the product ID and prepending it) distributes writes uniformly across splits, enabling high write throughput. Option D is correct because interleaved tables physically co-locate child rows with their parent row, so frequently joined data (such as inventory rows keyed to a product) is read with a single lookup rather than a distributed join, reducing latency and load. Option A is wrong because global secondary indexes are for query flexibility, not hotspot avoidance, and they add write amplification rather than improving throughput. Option B is wrong because a single table alone does not address key distribution; hotspots depend on the key structure, not the table count. Option E is wrong because a monotonically increasing integer primary key creates sequential writes that concentrate on the last split, which is the classic cause of hotspots in Cloud Spanner.

Answer

Use global secondary indexes only

Answer

Use a single table for all products

Answer

Use a monotonically increasing integer as the primary key

Question 6

A team uses Google Kubernetes Engine (GKE) with Node Auto-Provisioning. They want to optimize cost while maintaining high availability across zones. Which two strategies should they implement? (Select exactly 2.)

Accepted Answer

Use cluster autoscaler with appropriate min and max node counts. Option A is correct because the GKE cluster autoscaler adjusts the size of node pools between configured minimum and maximum node counts based on pending pod demand, so setting sensible min/max values prevents over-provisioning (cost savings) while the minimum keeps enough capacity for availability. Option B is correct because distributing node pools across multiple zones in a regional cluster ensures pods can be scheduled even if one zone fails, satisfying the high-availability requirement while still allowing the autoscaler to scale each zone's pool independently. Option C is wrong because preemptible (Spot) VMs can be reclaimed at any time with only a 30-second termination notice, which undermines high availability if used for all node pools. Option D is wrong because disabling the cluster autoscaler removes automatic scaling and would waste money on idle nodes or cause unschedulable pods. Option E is wrong because sole-tenant nodes provide physical isolation for compliance/licensing reasons, not high availability, and they are typically more expensive.

Answer

Use preemptible VMs for all node pools

Answer

Disable cluster autoscaler to prevent scaling

Answer

Use sole-tenant nodes for high availability

Question 7

A company is migrating from MySQL 5.7 to Cloud SQL for MySQL 8.0. They have stored procedures that use GROUP BY with non-aggregated columns. In MySQL 5.7, this is allowed. What change might they need to make?

Accepted Answer

Use ANY_VALUE() for non-aggregated columns in SELECT. MySQL 8.0 enables ONLY_FULL_GROUP_BY by default, which rejects queries that select non-aggregated columns not present in the GROUP BY clause. To keep the stored procedures working without rewriting the grouping logic, the engineer should wrap the non-aggregated columns in ANY_VALUE(), which tells MySQL to pick an arbitrary value from the group. This is the standard migration fix for this class of query.

Answer

Switch to Cloud Spanner

Answer

Downgrade to MySQL 5.7 on Cloud SQL

Answer

No changes needed; MySQL 8.0 is backward compatible

Question 8

A developer is using Firestore in Native mode for a mobile app. They want to secure data access based on user authentication. Which TWO mechanisms should they use? (Choose two)

Accepted Answer

Firestore Security Rules. Firebase Authentication (E) is the correct mechanism for authenticating end users of a mobile app, issuing ID tokens (JWTs) that identify the user to Firestore. Firestore Security Rules (A) are the server-side authorization layer that evaluates those tokens via request.auth and enforces per-document, per-field read/write conditions in Native mode. Together they provide the intended authentication-plus-authorization model for client access. Cloud Armor (B) is an edge WAF/DDoS service for HTTP(S) load balancers and does not govern Firestore document access. SSL/TLS in transit (C) is always-on transport encryption and does not implement user-based access control. IAM roles (D) govern administrative and server-side Google Cloud resource permissions, not per-user data access from mobile clients.

Answer

Cloud Armor

Answer

SSL/TLS encryption in transit

Answer

Cloud Identity and Access Management (IAM) roles

Question 9

Which Google Cloud database is best suited for high-throughput, low-latency caching to reduce load on a primary database?

Accepted Answer

Memorystore. Memorystore is Google Cloud's fully managed in-memory data store service, compatible with Redis and Memcached. It is designed for high-throughput, low-latency caching to reduce load on primary databases. By caching frequently accessed data in memory, it offloads read traffic from databases like Cloud SQL or Firestore, improving application performance and scalability.

Answer

Cloud SQL

Answer

Firestore

Answer

Cloud Bigtable

Question 10

A company is migrating a PostgreSQL application to AlloyDB for improved OLTP performance and the ability to run analytical queries on the same data. Which feature of AlloyDB BEST supports this hybrid HTAP workload?

Accepted Answer

Columnar engine. AlloyDB's columnar engine is specifically designed to accelerate analytical queries by storing data in a column-oriented format, which allows for faster scans and aggregations on large datasets. This enables the same database to handle both OLTP (row-oriented) and OLAP (column-oriented) workloads without requiring a separate analytics system, directly supporting the hybrid HTAP requirement described in the question.

Answer

In-database ML inference

Answer

Cross-region replication

Answer

Automatic storage scaling

Question 11

A team wants to monitor custom application metrics from a Compute Engine instance. They use the Cloud Monitoring agent. Which metric type should they use to report a gauge measurement like current memory usage?

Accepted Answer

gauge. A gauge metric type is specifically designed to report a value that can arbitrarily increase or decrease over time, such as current memory usage. The Cloud Monitoring agent supports gauge metrics for point-in-time measurements, and they are reported as a single data point without any aggregation window, making them ideal for snapshot-like observations.

Answer

histogram

Answer

delta

Answer

cumulative

Question 12

A company uses Cloud SQL MySQL for transactional workloads, BigQuery for analytics, and wants to stream real-time changes from Cloud SQL to BigQuery with minimal latency and no custom code. Which approach is most appropriate?

Accepted Answer

Use Datastream to capture CDC events from Cloud SQL MySQL and replicate them directly to BigQuery.. Datastream is purpose-built for minimal-latency, serverless change data capture (CDC) from sources like Cloud SQL MySQL to BigQuery. It uses log-based replication (reading the MySQL binary log) to stream row-level changes directly into BigQuery without requiring custom code or intermediate processing. This approach meets the requirements of real-time streaming with no custom code and minimal latency.

Answer

Set up a Cloud Function that queries Cloud SQL periodically and loads results into BigQuery via the streaming API.

Answer

Configure Cloud Scheduler to run an export of the Cloud SQL database every minute and load into BigQuery.

Answer

Create a Dataflow pipeline with a Pub/Sub topic and a change data capture connector for Cloud SQL.

Question 13

A team uses GitHub for source control. They want to automatically trigger Cloud Build builds on pull request creation. Which two actions are required? (Choose two.)

Accepted Answer

Install the Cloud Build GitHub app in the repository. Option A is correct because connecting a GitHub repository to Cloud Build requires installing the Cloud Build GitHub app (from the GitHub Marketplace) on the repository, which grants Cloud Build the webhook and OAuth permissions needed to receive repository events. Option B is correct because the trigger must be configured with the 'pull_request' event so Cloud Build fires when a pull request is created or updated, matching the team's requirement. Option C is wrong because Cloud Build's GitHub integration is handled by the GitHub app's automatic webhooks, not by manually configuring a webhook to send push events. Option D is wrong because mirroring GitHub into Cloud Source Repositories is unnecessary and would not by itself trigger builds on pull request creation. Option E is wrong because 'push' events and a 'pull-request/*' branch filter do not correspond to pull request creation; the correct event is 'pull_request'.

Answer

Configure a webhook in GitHub to send push events to Cloud Build

Answer

Use Cloud Source Repositories as a mirror of GitHub

Answer

In the Cloud Build trigger, set the event to 'push' and branch filter to 'pull-request/*'

Question 14

A team uses Cloud Build to deploy a microservice to Cloud Run. They want to enforce that only builds from the main branch trigger deployments to the production Cloud Run service. What is the best approach?

Accepted Answer

Use Cloud Build triggers with a branch filter set to ^main$.. Cloud Build triggers support a branch filter using a regular expression, so setting the filter to ^main$ ensures the trigger only fires for builds originating from the main branch. This is the native, declarative way to restrict deployments to production based on branch. It directly enforces the policy at the trigger level without manual intervention.

Answer

Configure Cloud Run to only accept revisions from a specific source repository.

Answer

Use IAM conditions on the Cloud Run service account to allow only main branch builds.

Answer

Create a separate Cloud Build trigger for each branch and manually disable non-main triggers.

Question 15

A team plans to migrate an Oracle database to Cloud SQL for PostgreSQL. They have identified complex PL/SQL packages that need conversion. Which open-source tool is specifically designed to assist with schema conversion from Oracle to PostgreSQL?

Accepted Answer

Ora2Pg. Ora2Pg is an open-source tool specifically designed to automate the migration of Oracle databases to PostgreSQL. It converts Oracle PL/SQL code, including complex packages, procedures, and functions, into PostgreSQL-compatible PL/pgSQL, and also handles schema objects like tables, views, sequences, and indexes. This makes it the correct choice for the team's need to convert complex PL/SQL packages.

Answer

Database Migration Service

Answer

pgloader

Answer

Liquibase