PCD Practice Test 49 — 15 Questions

Question 1

Which THREE of the following are best practices for building secure applications on Google Cloud?

Accepted Answer

Use Secret Manager to manage sensitive configuration values.. Secret Manager provides a centralized and secure way to store and manage sensitive configuration values such as API keys, database passwords, and certificates. By using Secret Manager, you avoid hardcoding secrets in source code or configuration files, reducing the risk of exposure. It integrates with IAM for fine-grained access control and supports automatic rotation, ensuring that secrets are protected at rest and in transit.

Answer

Disable authentication on a test Cloud Run service for end-user testing.

Answer

Use a single service account for all Cloud Functions to simplify permissions.

Question 2

During a code review, a developer notices that the application's Cloud Storage client library is using the default credentials of the Compute Engine instance. What is a more secure alternative for a production environment?

Accepted Answer

Create a dedicated service account with minimal permissions and attach it to the instance. Creating a dedicated service account with minimal permissions and attaching it to the Compute Engine instance follows the principle of least privilege. This avoids using the overly permissive default Compute Engine service account, which often has broad access to many Google Cloud services. By scoping the service account to only the required Cloud Storage permissions (e.g., roles/storage.objectViewer), you reduce the attack surface and adhere to production security best practices.

Answer

Store user credentials in a configuration file

Answer

Use an API key for Cloud Storage

Answer

Generate an access token and embed it in the code

Question 3

A mobile app developer wants a serverless NoSQL database that automatically syncs data offline and provides security rules for access control. Which Google Cloud database should they choose?

Accepted Answer

Firestore. Firestore is the correct choice: it is serverless, document-based, provides offline sync for mobile apps, and has Security Rules for access control.

Answer

Cloud Bigtable

Answer

Cloud Spanner

Answer

Memorystore for Redis

Question 4

A company is using Cloud Spanner for a global user database. They need to read recent orders for a user with strong consistency. The application currently uses stale reads with a max staleness of 10 seconds. Some users see inconsistent data. What is the BEST approach to guarantee strong consistency without significantly impacting latency?

Accepted Answer

Use strong reads with a read timestamp. Strong reads with a read timestamp ensure the most recent data. Bounded staleness is a weaker consistency model. Using DML or mutations does not affect read consistency.

Answer

Use global secondary indexes with STORING clause

Answer

Use mutations API instead of DML

Answer

Reduce max staleness to 1 second

Question 5

An e-commerce company is designing a global product inventory system that requires strong consistency across regions, horizontal scaling for millions of users, and 99.999% availability. Which Google Cloud database meets all these requirements?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only Google Cloud database that provides globally distributed ACID transactions with strong consistency, horizontal scaling, and 99.999% SLA.

Answer

Firestore

Answer

Cloud Bigtable

Answer

Cloud SQL for PostgreSQL

Question 6

A financial services company needs a globally distributed database that provides ACID transactions across regions with 99.999% availability SLA. The workload is transactional, with up to 10,000 transactions per second. Which database should they choose?

Accepted Answer

Cloud Spanner. Cloud Spanner offers global distribution, ACID transactions, and 99.999% SLA, making it ideal for financial transactional workloads.

Answer

Bigtable

Answer

Cloud SQL with cross-region replicas

Answer

Firestore in multi-region mode

Question 7

You are designing a Cloud Spanner schema with a parent Orders table and an OrderItems child table. Queries frequently join Orders and OrderItems on OrderId. Which feature should you use to optimize read performance?

Accepted Answer

Use interleaved tables with OrderItems as child of Orders. Interleaving stores child rows physically with the parent row, reducing latency for joins. Secondary indexes help lookups but not joins. Storing clause adds columns to index but does not improve join performance like interleaving.

Answer

Denormalize OrderItems into the Orders table

Answer

Use a STORING clause on the index

Answer

Create a global secondary index on OrderItems(OrderId)

Question 8

You need to create a Cloud Bigtable table to store time-series data for millions of IoT devices. Each device sends a reading every minute. You want to avoid hot spotting on row keys. Which row key design is recommended?

Accepted Answer

Use a row key composed of device ID followed by a reversed timestamp. Reversing the timestamp and prefixing with device ID spreads writes across tablets. Using only device ID or only timestamp causes hot spots.

Answer

Use the device ID as the row key

Answer

Use a reversed timestamp as the row key

Answer

Use a salted row key: device ID + hash of timestamp

Question 9

You are designing a Cloud Spanner schema with a parent table 'Customers' and a child table 'Orders'. To optimize read performance for retrieving a customer and their orders in a single split, you should use:

Accepted Answer

Interleaved tables with Customers as the parent. Interleaved tables store child rows with the parent row in the same split, enabling efficient joins and low-latency reads.

Answer

A secondary index on Orders.customer_id

Answer

A foreign key constraint from Orders to Customers

Answer

Use a single table with repeated fields

Question 10

A Cloud Spanner instance is experiencing high latency for global secondary index queries. The team notices that queries on the secondary index are performing full table scans instead of index scans. What is the most likely cause?

Accepted Answer

The index is a global index without the STORING clause, causing index join. In Cloud Spanner, secondary indexes can be local (interleaved with parent) or global (non-interleaved). If an index is defined as a global index, queries might still need to join with the base table unless the index includes all needed columns. Without the `STORING` clause, Spanner must fetch additional columns from the base table, causing the query to scan the base table.

Answer

The index is a local index without the STORING clause

Answer

The Spanner instance is under-provisioned

Answer

The index is defined on a composite key that is not selective

Question 11

A company wants to run HTAP workloads on a PostgreSQL-compatible database with a built-in columnar engine for faster analytics on transactional data. Which Google Cloud database should they choose?

Accepted Answer

AlloyDB. AlloyDB is a PostgreSQL-compatible database that includes a columnar engine for analytics, providing up to 4x faster OLTP than Cloud SQL PostgreSQL and is designed for hybrid HTAP workloads.

Answer

Cloud Spanner

Answer

Cloud SQL for PostgreSQL

Answer

BigQuery

Question 12

A team is designing a Cloud Spanner schema for a global user directory. To avoid write hotspots, which key design strategy should they use?

Accepted Answer

Use a composite primary key with a user ID and a hash prefix. Monotonically increasing keys like UUIDs or timestamps cause hotspots. Using a composite key with a hash prefix or swapping columns to distribute writes is recommended.

Answer

Use a UUID as the primary key

Answer

Use a timestamp as the primary key

Answer

Use a monotonically increasing integer as the primary key

Question 13

A team is designing a Firestore database for a global mobile game. They need to support offline play and sync data when the device is online. Which Firestore feature enables offline sync?

Accepted Answer

Offline persistence. Firestore provides persistent offline data access for mobile/web apps via built-in offline support in the client SDKs, enabling sync when connectivity returns.

Answer

Security Rules

Answer

Real-time listeners

Answer

Datastore mode

Question 14

You are designing a monitoring strategy for a microservices architecture running on GKE. Each service emits custom business metrics (e.g., order processing time). You want to create a dashboard that shows the 99th percentile latency for each service over the last 7 days. Which approach should you take?

Accepted Answer

Write custom metrics to Cloud Monitoring and create a dashboard with the 99th percentile aligner.. Cloud Monitoring supports custom metrics and provides built-in aligners, including a 99th percentile aligner, which can be applied directly in a dashboard chart. This allows you to compute the 99th percentile latency for each service over the last 7 days without manual calculation or exporting logs. Custom metrics are the appropriate mechanism for business metrics like order processing time, as they are designed for numeric time-series data.

Answer

Export logs to Cloud Logging and use Log Analytics to compute percentiles.

Answer

Use Metrics Explorer to view the metrics and manually compute percentiles.

Answer

Use Prometheus monitoring built into GKE and query the avg() function.

Question 15

You are designing a polyglot persistence architecture for an IoT platform. Device telemetry is stored in Cloud Bigtable for ingestion and low-latency queries. When a device registers a high-priority alert, you need to trigger an email notification. What is the recommended approach to decouple the alert processing from Bigtable?

Accepted Answer

Use the Bigtable change streams feature (currently in preview) to push alerts to Pub/Sub, then a Cloud Function sends the email.. Bigtable change streams (currently in preview) allow you to capture row-level changes in near real-time and publish them to Pub/Sub. This is the recommended approach to decouple alert processing from Bigtable. Using change streams, you can configure a subscription that triggers a Cloud Function to send the email notification. This pattern avoids the need for custom application code, polling, or inefficient batch processing. Option B (replication triggers) is not supported, option C adds unnecessary latency, and option D (polling) is inefficient and not decoupled.

Answer

Enable Bigtable replication and set up a trigger in the replica.

Answer

Write a Dataflow pipeline that reads from Bigtable and writes to Cloud Storage.

Answer

Create a scheduled Cloud Function that polls Bigtable every minute for new alerts.