PCD Practice Test 18 — 15 Questions

Question 1

Which Cloud Spanner configuration provides the highest availability and global read scalability?

Accepted Answer

Multi-region configuration. Multi-region configurations replicate data across multiple regions, providing higher availability and global read scalability compared to regional configurations.

Answer

Regional configuration with 1 read-write and 2 read-only replicas

Answer

Regional configuration with 3 read-write replicas

Answer

Single-zone configuration

Question 2

A company is migrating a MySQL OLTP database to Cloud SQL. The database has a peak of 10,000 read queries per second (QPS) and 2,000 write QPS. The team wants to reduce read latency and offload read traffic from the primary instance. Which TWO actions should they take? (Choose TWO.)

Accepted Answer

Create Cloud SQL read replicas in the same region. Cloud SQL supports read replicas (up to 10) that can serve read traffic, offloading the primary. Cross-region replicas increase latency. Using a Memorystore cache reduces repeated reads. Increasing primary machine type does not offload reads; it just scales the primary. Enabling automatic storage increase is for storage, not read performance.

Answer

Enable automatic storage increase on the primary

Answer

Create cross-region read replicas for geographic load balancing

Answer

Increase the machine type of the primary instance

Question 3

A DevOps team is troubleshooting high latency in a Cloud Bigtable instance. They notice that the row keys are lexicographically sorted timestamps. Which TWO actions will MOST improve performance? (Select 2 answers)

Accepted Answer

Use salt (hash prefix) in the row key. Adding a field promotion (e.g., user ID) to the row key distributes writes. Salting the row key with a hash prefix also distributes load. Adding nodes helps throughput but not the root cause.

Answer

Add more Bigtable nodes

Answer

Increase the number of column families

Answer

Enable compression on column families

Question 4

A company needs to run hybrid transactional/analytical processing (HTAP) workloads on a PostgreSQL-compatible database. They want to use in-database ML inference and require 4x faster OLTP performance compared to standard PostgreSQL. Which database should they choose?

Accepted Answer

AlloyDB for PostgreSQL. AlloyDB is PostgreSQL-compatible, offers a columnar engine for fast analytics, supports in-database ML, and claims up to 4x faster OLTP than Cloud SQL PostgreSQL.

Answer

BigQuery

Answer

Cloud SQL for PostgreSQL

Answer

Cloud Spanner

Question 5

A company needs to store petabytes of time-series IoT sensor data and query it with single-digit millisecond latency at millions of reads per second. The data has a simple key-value structure with timestamps. Which Google Cloud database is MOST appropriate?

Accepted Answer

Cloud Bigtable. Cloud Bigtable is designed for petabyte-scale, low-latency, high-throughput NoSQL storage for time-series, IoT, and financial data.

Answer

BigQuery

Answer

Cloud Spanner

Answer

Firestore

Question 6

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. Using a composite key with a hash prefix distributes writes. Interleaved tables store child rows with parent, reducing cross-split operations. Monotonically increasing keys cause hotspots.

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 7

A company is building a polyglot persistence architecture. They need to choose the correct Google Cloud databases for the following requirements: (1) ACID transactions for financial orders, (2) high-throughput time-series sensor data, and (3) real-time session cache. Which THREE databases should they choose? (Choose 3)

Accepted Answer

Memorystore. Cloud Spanner provides ACID transactions globally, Bigtable for time-series, and Memorystore for caching. Firestore is document-oriented, not ideal for time-series.

Answer

Cloud SQL

Answer

Firestore

Question 8

A company uses Cloud Spanner for global transaction processing. They need to export a full database backup to GCS in a portable format for long-term archival. Which method should they use?

Accepted Answer

Use Cloud Spanner backups (built-in) which export to GCS in Avro format.

Answer

Use gcloud beta spanner databases export command to export to GCS in CSV format.

Answer

Use Dataflow to read the Spanner database and write to GCS in JSON format.

Answer

Use Cloud SQL export to GCS.

Question 9

A company runs a global stock trading platform that requires strong consistency across regions. They need to read the latest account balance after each trade. Which Cloud Spanner read mode should they use?

Accepted Answer

Strong reads. Strong reads provide the latest committed data with global consistency. Stale reads (bounded staleness) may return older data. External consistency is a Spanner property but not a read mode.

Answer

Read-only transactions with external consistency

Answer

Stale reads with bounded staleness of 10 seconds

Answer

Bounded staleness reads with max staleness of 1 second

Question 10

A company needs to run analytics on their Cloud SQL database without affecting OLTP performance. They want to use a read replica. What is the BEST practice?

Accepted Answer

Create a read replica in the same or different region and route analytics queries to it. Using a cross-region read replica can offload analytics queries without impacting the primary instance, but for read scalability within region, an in-region replica works too.

Answer

Run analytics directly on the primary instance

Answer

Export the data to BigQuery periodically

Answer

Use Cloud SQL's HA instance for analytics

Question 11

Which Google Cloud database service provides a fully managed, in-memory caching solution compatible with the Redis protocol?

Accepted Answer

Memorystore for Redis. Memorystore for Redis provides a managed Redis service for caching, session stores, and pub/sub messaging.

Answer

Firestore

Answer

Bigtable

Answer

Cloud SQL

Question 12

An e-commerce platform uses Cloud Spanner for order processing and BigQuery for analytics. The team needs to capture all changes in the Spanner 'Orders' table and stream them to Pub/Sub for downstream processing. Which Spanner feature should be used?

Accepted Answer

Configure Spanner change streams. Cloud Spanner change streams capture all data changes in a database or table and can be read via Pub/Sub or Dataflow. This is the native way to stream changes from Spanner.

Answer

Export to GCS using the console

Answer

Use Spanner Interleaved tables

Answer

Create a Cloud Function triggered by Spanner

Question 13

A financial services company uses Cloud SQL for MySQL for transactional data. They need to analyze this data in BigQuery without moving data or impacting transactional performance. Which approach should they use?

Accepted Answer

Create a BigQuery federated query to Cloud SQL MySQL using an external table

Answer

Set up Cloud SQL replication to a read replica and connect BigQuery to it

Answer

Export Cloud SQL data to GCS as CSV and load into BigQuery daily

Answer

Use Datastream to replicate Cloud SQL data to BigQuery in real-time

Question 14

A Cloud Bigtable instance is experiencing high latency for reads of recent data. The row keys start with a timestamp. What is the MOST likely cause?

Accepted Answer

Row key design leading to hotspotting. Using timestamp as the leading part of the row key causes all recent writes to go to a single tablet server, creating a hotspot.

Answer

Too many column families

Answer

Garbage collection policy too aggressive

Answer

Insufficient number of nodes

Question 15

An application needs a low-latency in-memory cache to reduce database load and improve response times. The cache must support pub/sub messaging and rate limiting. Which GCP service should be used?

Accepted Answer

Memorystore for Redis. Memorystore for Redis provides in-memory caching, pub/sub, and rate limiting capabilities. Memcached does not support pub/sub.

Answer

Firestore

Answer

Cloud SQL

Answer

Memorystore for Memcached