PCD Practice Test 26 — 15 Questions

Question 1

An e-commerce platform uses Cloud Spanner for order management and Bigtable for product recommendations. They need to replicate order changes to the Bigtable cluster in real-time for updating recommendations. The team must ensure that all order updates are captured and delivered exactly once, in order, to the Bigtable pipeline. Which THREE components should they use?

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

Accepted Answer

Cloud Spanner Change Streams. Spanner change streams capture all data changes (inserts, updates, deletes) and can publish to Pub/Sub. Dataflow can consume these messages and write to Bigtable with exactly-once processing. Pub/Sub provides ordered delivery when using message ordering. Cloud Tasks is not suitable for high-throughput streaming. Cloud Functions would be too slow and less reliable for exactly-once. BigQuery is not needed.

Answer

Cloud Tasks

Answer

Cloud Functions

Question 2

A company is using Bigtable for real-time analytics and notices that certain row keys are causing hot spots. Which tool should they use to identify the hot spot patterns?

Accepted Answer

Key Visualizer. Bigtable Key Visualizer is designed to analyze access patterns and identify hot spots by visualizing row key distribution and traffic. It helps optimize row key design. The other options are general monitoring or optimization tools not specific to Bigtable key analysis.

Answer

Profiler

Answer

Cloud Monitoring workspace

Answer

Cloud Trace

Question 3

A company is deploying a new financial application on Google Cloud that requires strong consistency, global scale, and the ability to handle millions of transactions per second across multiple regions. The application data has a relational structure. Which database service should they choose?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only Google Cloud database that provides global strong consistency, horizontal scaling, and relational schema support at massive transaction volumes. Cloud SQL is limited to a single region, Bigtable does not support relational data, and Firestore is document-based with limited transaction support.

Answer

Firestore

Answer

Cloud SQL for MySQL

Answer

Cloud Bigtable

Question 4

A company is designing a Cloud Bigtable schema for a time-series application. The application writes data from millions of devices and reads recent data by device ID and time range. Which TWO design patterns should they implement to optimize performance? (Select TWO.)

Accepted Answer

Use a single table with a row key that combines device_id and reversed timestamp. To optimize reads by device ID and time range, promote device_id to the start of the row key for efficient scans. Reverse the timestamp to avoid hotspotting on recent writes. Column families separate access patterns but don't affect read efficiency directly. A single table is fine.

Answer

Use multiple tables, one per device

Answer

Use a salting prefix to distribute writes

Answer

Store frequently accessed columns in a separate column family from rarely accessed ones

Question 5

A manufacturing company collects time-series data from thousands of sensors and wants to store it in Cloud Bigtable. They need to design a row key that avoids hotspots and ensures even distribution of writes across tablets. Which row key design strategy is BEST?

Accepted Answer

Prefix the timestamp with a hash of the sensor ID. To avoid hotspots, the row key should start with a field that has high cardinality and even distribution. A common approach is to prepend a hash or a nonce derived from the timestamp or sensor ID to spread writes across tablets.

Answer

Use an inverted timestamp as the row key

Answer

Use the sensor ID as the first component of the row key

Answer

Use a single row key for all data from the same day

Question 6

A company wants to deploy a database for a global application that requires strong consistency across continents, with the ability to handle millions of reads and writes per second. Which Google Cloud database should they choose?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only globally distributed, strongly consistent relational database that can handle millions of operations per second across multiple continents.

Answer

Firestore

Answer

Cloud SQL

Answer

Cloud Bigtable

Question 7

You are designing a Cloud Spanner schema for a global user profile table. User IDs are integers from a sequence. You need to avoid hot spots during writes. Which primary key design is best?

Accepted Answer

Use a composite primary key: (HashPrefix(UserId), UserId) where HashPrefix is from a small set. Using a composite key with a hash prefix spreads writes across splits evenly. Sequential integer keys cause hot spots on the last split.

Answer

Use a UUID as the primary key

Answer

Use the sequential integer user ID alone as the primary key

Answer

Use a timestamp as the primary key

Question 8

A company is using Cloud Bigtable for an ad-tech application with billions of ad impressions per day. They need to perform point reads on individual rows as well as scans over time ranges. Which column family design is recommended?

Accepted Answer

Separate frequently accessed columns into one column family and infrequently accessed into another. To optimize performance, frequently accessed columns (e.g., for point reads) should be in a separate column family from infrequently accessed columns (e.g., audit data). This reduces the amount of data scanned during scans and improves cache efficiency.

Answer

Use multiple tables for different access patterns

Answer

Store each column as a separate column family

Answer

Store all columns in a single column family for simplicity

Question 9

A company needs to secure their Cloud SQL for MySQL instance. They want to ensure that only applications running within their VPC can connect, and that all connections are encrypted. Which two steps should they take? (Choose two.)

Accepted Answer

Enable the 'require_ssl' flag. Using private IP restricts connections to the VPC, and enabling SSL enforcement ensures encryption. IAM authentication is additional but not required for VPC-only connectivity.

Answer

Use Cloud SQL Auth Proxy on the application side

Answer

Assign a public IP address to the instance

Answer

Enable IAM database authentication

Question 10

An organization uses Cloud Spanner in a multi-region configuration. They want to monitor performance and identify potential bottlenecks. Which three metrics should they review? (Choose three.)

Accepted Answer

Read and write latency. Processing units utilization indicates capacity, read/write latency measures performance, and high-priority CPU target helps identify contention. Rows deleted is not a performance metric.

Answer

Disk bytes used

Answer

Rows deleted by deletes

Question 11

An organization runs a MySQL database on Cloud SQL. They want to ensure that all connections to the database are encrypted. Which action should they take?

Accepted Answer

Set the 'require_ssl' flag on the Cloud SQL instance to 'on'. Enabling the 'require_ssl' flag ensures that only SSL/TLS connections are accepted, enforcing encryption for all client connections.

Answer

Use the Cloud SQL Auth Proxy

Answer

Enable IAM database authentication

Answer

Create the instance with the '--require-ssl' flag

Question 12

A company is using Cloud SQL for MySQL and wants to offload read traffic to a replica for better performance. They also need the replica to be available for disaster recovery in a different region. What should they do?

Accepted Answer

Create a cross-region read replica in another region.. Cross-region read replicas serve both read scaling and disaster recovery. They can be promoted to primary in a different region. Same-region replicas do not protect against regional failures. External replicas are not necessary; Cloud SQL supports cross-region replicas natively.

Answer

Enable high availability on the primary instance.

Answer

Create a same-region read replica and use failover.

Answer

Use an external replica in another region via MySQL replication.

Question 13

A financial services company requires a globally distributed database with strong consistency and sub-10 millisecond write latency across three continents. They anticipate 50 TB of transactional data. Which Google Cloud database should they deploy?

Accepted Answer

Cloud Spanner multi-region configuration. Cloud Spanner is the only Google Cloud database that provides global strong consistency, horizontal scaling, and low-latency reads and writes across regions. Multi-region configurations span continents and meet the requirements.

Answer

Firestore in multi-region mode

Answer

Cloud Bigtable with multi-cluster replication

Answer

Cloud SQL with cross-region replicas

Question 14

A social media company is building a real-time analytics platform to process user activity streams. They need to ingest millions of events per second, store them for 30 days, and query with sub-10ms latency. Which TWO Google Cloud services should they use together? (Choose 2)

Accepted Answer

Cloud Pub/Sub. Cloud Pub/Sub is ideal for ingesting high-throughput event streams, and Cloud Bigtable provides low-latency storage and querying. Together they meet the requirements.

Answer

Firestore

Answer

Cloud Spanner

Answer

BigQuery

Question 15

An engineer needs to create a Cloud SQL instance for a development environment with minimal cost. The instance will have low traffic, and storage growth is expected to be gradual. Which storage configuration should they choose?

Accepted Answer

Use SSD storage with storage auto-increase enabled.. SSD storage is recommended for most workloads due to performance, and enabling auto-increase ensures you don't run out of disk. HDD is cheaper but has much lower IOPS, which may cause performance issues even for dev. Disabling auto-increase risks downtime. The smallest disk size with SSD and auto-increase is cost-effective.

Answer

Use HDD storage with storage auto-increase disabled.

Answer

Use SSD storage with storage auto-increase disabled.

Answer

Use HDD storage with storage auto-increase enabled.