PCD Practice Test 27 — 15 Questions

Question 1

A company uses Cloud Bigtable for time-series data. They notice uneven load distribution across nodes causing hot spots. Which tool should they use to identify the hot spots?

Accepted Answer

Cloud Bigtable Key Visualiser. Cloud Bigtable Key Visualiser graphically shows read/write heatmaps to identify hot spots. Monitoring dashboards show metrics but not specific hot spots. cbt tool is CLI, not visual. Cloud Logging records operations but doesn't visualize load distribution.

Answer

Cloud Monitoring dashboards

Answer

cbt command-line tool

Answer

Cloud Logging

Question 2

A company uses AlloyDB for PostgreSQL and needs to scale read traffic automatically. They also want to ensure the database remains available if the primary zone fails. Which two features should they use? (Choose two.)

Accepted Answer

Configure the cluster as a regional cluster with high availability. Read pool instances provide auto-scaling read replicas, and regional cluster with HA provides automatic failover across zones.

Answer

Deploy AlloyDB Omni on-premises

Answer

Use a single-zone cluster and rely on read replicas for HA

Answer

Enable cross-region replication

Question 3

A company uses Cloud SQL for MySQL with a single zone. They need high availability with automatic failover in under 60 seconds. What configuration should they use?

Accepted Answer

Enable regional HA by adding a standby in a different zone. Cloud SQL HA configuration creates a primary and a standby instance in different zones within the same region, using synchronous replication. Automatic failover occurs in under 60 seconds. Zonal HA is not a valid concept, and cross-region failover is not automatic.

Answer

Configure zonal HA with a standby in the same zone

Answer

Use AlloyDB with cross-region replication

Answer

Create a read replica in a different region

Question 4

An engineer is designing a disaster recovery strategy for a Cloud SQL for SQL Server instance. They need to be able to fail over to a different region with minimal data loss. Which TWO actions should they take? (Choose two.)

Accepted Answer

Create a cross-region read replica.. Cross-region replicas provide asynchronous replication to another region, allowing promotion for DR. Point-in-time recovery can be used to restore to the latest state before a disaster, minimizing data loss. HA is zone-level, not cross-region. Export/import is not real-time. Backup is point-in-time but not continuous replication.

Answer

Export the database daily to Cloud Storage.

Answer

Use an external replica in another region.

Answer

Enable high availability (regional) on the primary instance.

Question 5

A company is designing a Cloud Spanner schema for a global user database. They anticipate high write throughput and want to avoid hotspotting on the primary key. Which primary key design strategy is MOST appropriate?

Accepted Answer

Use a UUID as the primary key. Using a composite key with a hash prefix or a monotonically increasing value as the first part of the key can cause hotspots. UUIDs distribute writes evenly across splits. Using a UUID as the leading part of a composite key avoids hotspotting better than the other options.

Answer

Use an auto-incrementing integer as the primary key

Answer

Use a timestamp as the primary key

Answer

Use a composite key with user_id and timestamp

Question 6

A company is using Cloud Bigtable to serve real-time analytics. They notice that some queries are slow, and the Key Visualizer shows a narrow row key range receiving the majority of reads and writes. What is the most likely cause and recommended action?

Accepted Answer

A single row key prefix is being accessed heavily, causing a hot spot; redesign the row key to distribute load. Hot spotting occurs when a small range of row keys is heavily accessed, causing uneven load distribution. Using a well-distributed row key design (e.g., salting) is the recommended solution.

Answer

The cluster has too few nodes; add more nodes to the cluster

Answer

Enable replication to a secondary cluster to offload reads

Answer

The storage type is HDD; switch to SSD to improve latency

Question 7

An e-commerce platform uses Memorystore for Redis as a session store. During a flash sale, the application experiences high latency and some sessions are evicted. The application currently uses a Standard Tier instance with 5 GB of memory. What is the MOST effective solution to improve performance and prevent evictions?

Accepted Answer

Increase the instance memory to 10 GB and enable persistence. Memorystore for Redis has two tiers: Basic (no replication, no HA) and Standard (replicated, HA). Basic tier does not support replication or high availability. Increasing memory to 10 GB provides more room for session data, preventing evictions. Using a larger machine type with additional memory is the correct remedy for evictions. Changing to Basic tier would worsen availability. Using a cache aside pattern is a client-side optimization, not directly addressing evictions. Deleting unused keys may free space but is not a scalable solution.

Answer

Switch from Standard Tier to Basic Tier to reduce overhead

Answer

Delete all unused keys hourly using a scheduled job

Answer

Implement a cache-aside pattern with Cloud Firestore

Question 8

A mobile app needs to store user preferences as a simple key-value store. The data is infrequently accessed and should be highly available with no operational overhead. The app is already using Firebase. Which database is the best fit?

Accepted Answer

Firestore. Firestore is serverless, integrates with Firebase, and is ideal for storing user preferences as documents.

Answer

Bigtable

Answer

Memorystore

Answer

Cloud SQL

Question 9

A company is migrating from MySQL 5.7 to Cloud SQL for MySQL 8.0. They have a mix of MyISAM and InnoDB tables, and their application uses utf8 charset. They want to minimize changes to the application code. Which THREE changes should they make during migration? (Choose 3 options.)

Accepted Answer

Convert all MyISAM tables to InnoDB.. MySQL 8.0 changes default authentication to caching_sha2_password, which may break application connections if the client driver does not support it. MyISAM tables should be converted to InnoDB for reliability and features like foreign keys. utf8 charset should be changed to utf8mb4 to avoid truncation of 4-byte characters. The caching_sha2_password plugin is default; if the app uses older connectors, they may need to set the default to mysql_native_password or update the connector.

Answer

Keep utf8 charset to avoid application code changes.

Answer

Keep the default authentication plugin as caching_sha2_password.

Question 10

A company is migrating an on-premises Oracle database to Google Cloud. They need a managed relational database with high availability, but they are not ready to redesign their schema for sharding. They also want to reduce licensing costs. Which TWO Google Cloud database services should they consider? (Choose 2)

Accepted Answer

Cloud SQL for SQL Server. Cloud SQL supports managed MySQL, PostgreSQL, and SQL Server, suitable for lift-and-shift. AlloyDB is PostgreSQL-compatible and offers high performance with a columnar engine. Both are managed and reduce licensing costs compared to Oracle.

Answer

Firestore

Answer

Cloud Spanner

Answer

Bigtable

Question 11

A gaming company wants to store player profiles and game state data that require strong consistency and the ability to run SQL queries. They also need to support real-time leaderboards with high write throughput. Which two Google Cloud databases should they consider? (Choose 2)

Accepted Answer

Memorystore for Redis. Cloud Spanner provides strong consistency and SQL, while Memorystore for Redis can be used for real-time leaderboards with high throughput. Bigtable and Firestore do not have SQL, and AlloyDB is not ideal for high-throughput leaderboards.

Answer

Cloud Bigtable

Answer

AlloyDB

Answer

Firestore

Question 12

You are tuning a Cloud Bigtable table used for analytics. One column family, 'data', contains both frequently accessed columns (e.g., 'price', 'volume') and rarely accessed columns (e.g., 'raw_json'). To optimize performance and cost, what column family design is recommended?

Accepted Answer

Create two column families: 'core' for frequently accessed columns and 'extended' for rarely accessed columns. Separating columns into different column families based on access patterns is a best practice. Frequently accessed columns should be in one column family (e.g., 'core'), and rarely accessed columns in another (e.g., 'extended'). This allows Bigtable to optimize storage and read performance.

Answer

Use separate tables for each access pattern

Answer

Store rarely accessed columns as a JSON string in a single column

Answer

Place all columns in a single column family for simplicity

Question 13

An organization uses Flyway for versioned schema migrations. They are migrating from PostgreSQL to Cloud SQL for PostgreSQL. What is the best practice for applying schema changes during the migration?

Accepted Answer

Use Flyway migration scripts in a CI/CD pipeline. Flyway integrates well with Cloud SQL and CI/CD. The best practice is to use Flyway migrations to apply schema changes before or after data migration, ensuring version control and repeatability.

Answer

Use Database Migration Service to apply schema changes

Answer

Manually apply schema changes using pgAdmin

Answer

Use Cloud SQL import wizard

Question 14

A healthcare company uses Cloud SQL for PostgreSQL to store patient records. They need to implement a disaster recovery plan with cross-region failover capability and minimal data loss. Which TWO steps should they take? (Choose two)

Accepted Answer

Enable automated backups and point-in-time recovery. Cross-region read replicas can be promoted in a disaster, but they may have data loss. To minimize loss, use Cloud SQL HA in the primary region plus a cross-region read replica. Automated backups provide point-in-time recovery but not automatic failover.

Answer

Migrate to Cloud Spanner for multi-region support

Answer

Use Cloud SQL HA instance in the primary region

Answer

Enable cross-region replication using Cloud SQL's built-in feature

Question 15

A company needs a managed Redis instance for caching and pub/sub messaging in their application. Which Google Cloud service should they use?

Accepted Answer

Memorystore for Redis. Memorystore for Redis is a managed Redis service that supports caching and pub/sub. Memorystore for Memcached only supports caching. Cloud SQL and Firestore are not caching services.

Answer

Firestore

Answer

Cloud SQL

Answer

Memorystore for Memcached