PCDE Plan and manage database infrastructure Practice Test 6 — 15 Questions

Question 1

Refer to the exhibit. The company plans to store 3 TB of data in this instance. What is the minimum number of nodes required? (Assume 2 TB per node for HDD and 4 TB per node for SSD; this instance uses SSD.)

Accepted Answer

2. The instance uses SSD storage, which provides 4 TB per node. To store 3 TB of data, a single node with 4 TB SSD would suffice, but the question asks for the minimum number of nodes required. However, the correct answer is 2 because in a distributed database like Couchbase (commonly tested in PCDE), data is replicated across nodes for high availability and durability. With 1 node, there is no redundancy; with 2 nodes, you can store 3 TB of data while maintaining a replica, as each node contributes 4 TB of usable storage, and the effective storage after replication is 4 TB (2 nodes × 4 TB / 2 replicas = 4 TB), which is sufficient for 3 TB.

Answer

4

Answer

1

Answer

3

Question 2

Refer to the exhibit. The application requires low-latency reads for users in Europe. The current cluster is in us-central1. What should they do?

Accepted Answer

Add a new cluster in a European region (e.g., europe-west1).. Adding a new cluster in a European region (e.g., europe-west1) is correct because it places data physically closer to users, reducing network latency for read operations. In a multi-region deployment, the application can read from the nearest cluster, achieving low-latency reads without changing the existing cluster's configuration. This approach leverages geographic proximity to minimize round-trip time (RTT) for European users.

Answer

Increase the number of nodes in the existing cluster.

Answer

Use a multi-cluster instance with existing cluster.

Answer

Change the storage type to SSD in the existing cluster.

Question 3

A company is migrating their on-premises PostgreSQL database to Cloud SQL. They want to minimize downtime during the migration. Which approach should they use?

Accepted Answer

Use Database Migration Service with continuous replication. Database Migration Service (DMS) with continuous replication is the correct approach because it uses change data capture (CDC) to replicate ongoing transactions from the source PostgreSQL database to Cloud SQL, enabling a near-zero downtime migration. DMS handles schema conversion, data validation, and automated failover, which minimizes the cutover window to seconds or minutes.

Answer

Use pg_dump and pg_restore

Answer

Export data to CSV and import into Cloud SQL

Answer

Use a third-party ETL tool

Question 4

You need to transfer 10 TB of data from on-premises servers to Cloud Storage for loading into Bigtable. Which method is the most efficient and reliable for this volume?

Accepted Answer

Use Storage Transfer Service. The Storage Transfer Service is designed for large-scale, online data transfers from on-premises or other cloud providers to Google Cloud. It handles 10 TB efficiently by automatically managing retries, checksums, and network optimization without requiring manual scripting or persistent VPN connections, making it the most reliable and efficient choice for this volume.

Answer

Set up Cloud VPN and use rsync

Answer

Use gsutil cp in parallel

Answer

Use Dataflow to read and write data

Question 5

A Cloud SQL for MySQL instance requires a patch update. How can you minimize downtime during the update?

Accepted Answer

Schedule the maintenance during a maintenance window. Option D is correct because Cloud SQL for MySQL uses a maintenance window to schedule patching during a period of low traffic, minimizing user impact. While a restart is typically required for patch application, the maintenance window allows you to control when that restart occurs, reducing downtime exposure. This is the standard recommended approach for managed database patching in Google Cloud.

Answer

Apply the patch without restart

Answer

Use database migration to a new instance

Answer

Failover to a read replica during the update

Question 6

A company needs to store time-series sensor data with high write throughput (millions of writes per second) and low latency reads. Which database service should they choose?

Accepted Answer

Cloud Bigtable. Cloud Bigtable is a fully managed, scalable NoSQL database designed for large analytical and operational workloads, handling millions of writes per second with consistent low-latency reads. It uses a distributed, replicated SSTable storage engine and is optimized for time-series data, making it ideal for high-throughput sensor ingestion.

Answer

Cloud SQL

Answer

Firestore

Answer

Cloud Spanner

Question 7

You need to export data from Cloud Spanner for archival purposes. Which method is most cost-effective?

Accepted Answer

Use gcloud spanner databases export. Option A is correct because the native gcloud spanner databases export command exports data directly to Cloud Storage with minimal cost and no additional compute resources. Options B and D (Dataflow, Cloud Function) incur additional compute charges. Option C (execute-sql) is not suitable for full database export.

Answer

Use a Cloud Function to copy data

Answer

Use Dataflow to read and write to Cloud Storage

Answer

Use gcloud spanner databases execute-sql

Question 8

A Cloud SQL for PostgreSQL instance is experiencing high CPU usage due to many short-lived connections. Which configuration change can help without application changes?

Accepted Answer

Enable connection pooling with pgBouncer. Option B is correct because enabling connection pooling with pgBouncer reduces the CPU overhead of creating and tearing down connections. Option A (read replicas) helps with read load, not CPU from connections. Option C (increase max_connections) may worsen the issue. Option D (increase tier) increases cost but may not address the root cause of connection churn.

Answer

Use read replicas

Answer

Increase the max_connections parameter

Answer

Increase the tier to more vCPUs

Question 9

You need to ensure that read operations on a Cloud Spanner database return the most recent committed data. Which read type should you use?

Accepted Answer

Strong read. Strong read is the correct choice because it guarantees that read operations return the most recent committed data from Cloud Spanner. Unlike other read types, strong reads access the current state of the database at the time of the read, ensuring external consistency and linearizability, which is critical for applications requiring up-to-date data.

Answer

Read-only transaction

Answer

Stale read

Answer

Partitioned read

Question 10

You are building a globally distributed leaderboard application that requires strongly consistent reads with latency under 10 ms and high write throughput. Which Google Cloud database service is most suitable?

Accepted Answer

Cloud Spanner. Cloud Spanner is the correct choice because it provides strongly consistent reads across globally distributed regions with latency under 10 ms, while also supporting high write throughput. It uses TrueTime and synchronous replication to ensure ACID transactions and global consistency, meeting the exact requirements of a globally distributed leaderboard application.

Answer

Cloud Bigtable

Answer

Memorystore

Answer

Firestore

Question 11

A Cloud SQL instance is running low on disk space. You want to increase disk size with zero downtime. Which action should you take?

Accepted Answer

Use gcloud sql instances patch to increase the storage size. Option D is correct because Cloud SQL supports online storage increases without downtime. The `gcloud sql instances patch` command (or the equivalent Console/API operation) dynamically adds more disk capacity to the running instance while it continues serving traffic. This is possible because Cloud SQL uses persistent disks that can be resized online, and the database engine (e.g., MySQL, PostgreSQL) does not need to restart to recognize the additional space.

Answer

Stop the instance, increase disk, and restart

Answer

Export data, create a new instance with larger disk, and import

Answer

Create a clone with larger disk and failover

Question 12

You are designing a highly available Cloud SQL for MySQL architecture. Which TWO components are essential?

Accepted Answer

High availability (HA) configuration with a standby zone. A is correct because Cloud SQL for MySQL High Availability (HA) configuration provisions a standby instance in a different zone within the same region, enabling automatic failover with minimal downtime. B is correct because regional persistent disks replicate data synchronously across two zones, ensuring data durability and availability even if an entire zone fails, which is a prerequisite for HA.

Answer

Point-in-time recovery (PITR)

Answer

Read replicas in the same region

Answer

Cross-region replication

Question 13

You are planning capacity for a Cloud Spanner instance. Which TWO factors directly affect the number of nodes required?

Accepted Answer

Read throughput in queries per second (QPS). Cloud Spanner node capacity is primarily determined by compute and I/O requirements, which are directly driven by read and write throughput (QPS). Each node provides a fixed amount of processing power and throughput; therefore, to handle a given QPS, you must provision enough nodes to meet the peak read and write demand. Storage size (Option E) is not a direct factor because Spanner automatically uses available node resources for storage, and you can add nodes for throughput without exceeding storage limits.

Answer

Number of users

Answer

Number of indexes

Answer

Storage size in GB

Question 14

A company is planning to migrate their on-premises Oracle database to Cloud SQL. Which THREE prerequisites must be satisfied?

Accepted Answer

Convert Oracle-specific syntax to PostgreSQL or MySQL. Option A is correct because Cloud SQL does not support Oracle's proprietary PL/SQL syntax. When migrating from Oracle to Cloud SQL, you must convert Oracle-specific syntax (e.g., sequences, packages, hierarchical queries) to the target dialect—either PostgreSQL or MySQL—since Cloud SQL offers only these two engines. This conversion is a prerequisite to ensure the migrated database functions correctly after the move.

Answer

Purchase Cloud SQL Enterprise Plus edition for the target instance

Answer

Create a Cloud Storage bucket for staging migration data

Question 15

Refer to the exhibit. This DDL is used to create a table in Cloud Spanner. The table will be used for storing user data with high write throughput. What is one performance issue with this table design?

Accepted Answer

The primary key is a monotonically increasing integer. Option A is correct because a monotonically increasing primary key (UserId) causes hot spots as all writes concentrate on the last split. Option B (STRING(MAX)) is acceptable but not a performance issue. Option C (no indexes) is not required for write throughput. Option D (not interleaved) is irrelevant.

Answer

The Name column is of type STRING(MAX)

Answer

There are no secondary indexes

Answer

The table is not interleaved with another table

PCDE Plan and manage database infrastructure Practice Test 6 — 15 Questions

Exhibit

PCDE Plan and manage database infrastructure Practice Test 6 — 15 Questions

Exhibit