PCDE Practice Test 5 — 25 Questions

Question 1

Your company runs a critical PostgreSQL database on Cloud SQL. You need to minimize downtime during a schema migration that could take up to 30 minutes. What should you do?

Accepted Answer

Create a clone of the instance, perform the migration on the clone, then promote the clone.. Creating a clone of the Cloud SQL instance allows you to perform the schema migration on an isolated copy without affecting the production database. Once the migration is complete and verified, you can promote the clone to take over as the primary instance, minimizing downtime to just the brief promotion switchover (typically seconds). This approach avoids the long 30-minute migration window on the live database.

Answer

Use Database Migration Service to migrate to a new instance during the migration window.

Answer

Configure a high-availability instance and perform the migration during a planned failover.

Answer

Add a read replica, perform the migration on the replica, then promote it.

Question 2

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 exactly this use case — petabyte-scale, low-latency (single-digit ms), high-throughput NoSQL storage for time-series, IoT, and financial data. It scales horizontally by adding nodes. BigQuery is optimised for analytics (seconds-to-minutes latency), Cloud SQL is for OLTP (limited to tens of thousands of QPS), and Firestore is for document data with hierarchical structure.

Answer

Firestore

Answer

Cloud Spanner

Answer

BigQuery

Question 3

A company needs to control cost by setting a budget alert on their billing account. They want to be notified when spending exceeds 80% of the budget. What should they configure?

Accepted Answer

Create a budget in the GCP Billing console with alert threshold at 80%.. Google Cloud's native budget alerts in the Billing console allow you to set a threshold (e.g., 80%) and automatically send email notifications when actual spending exceeds that percentage of the budget. This is the simplest, most direct, and recommended approach for cost control without needing additional services or custom code.

Answer

Export billing data to BigQuery and set up a scheduled query with a Cloud Function to send alerts.

Answer

Create a budget alert rule in Cloud Monitoring with a metric threshold.

Answer

Use Cloud Scheduler to run a script that checks billing API and sends email.

Question 4

Your Firestore database in Native mode is used by a mobile app. You need to query a collection where documents are filtered by two fields: 'status' (string) and 'createdAt' (timestamp). The query is not performing as expected. What action is required?

Accepted Answer

Create a composite index on the 'status' and 'createdAt' fields.. Firestore in Native mode requires a composite index to efficiently query documents filtered by multiple fields, such as 'status' and 'createdAt'. Without this index, the query may fail or perform poorly, as Firestore cannot combine separate single-field indexes for equality and range filters. Option C is correct because creating a composite index on both fields enables the query to run as expected.

Answer

Create an index exemption for the collection to allow multi-field queries.

Answer

Add a third field to the query to make it more specific.

Answer

Ensure that single-field indexes exist for both 'status' and 'createdAt'.

Question 5

A DevOps engineer is designing a landing zone for a large enterprise. Which THREE components are essential for a well-architected landing zone? (Choose THREE.)

Accepted Answer

A shared VPC project to host common network resources.. A landing zone typically includes a shared VPC for network connectivity, a centralized logging project for audit logs, and a security project for centralized security services like Cloud Armor and Security Command Center.

Answer

A single billing account per team.

Answer

A separate project per developer for sandbox environments.

Question 6

An e-commerce platform uses Cloud Spanner with a table Orders and a child table OrderItems. The primary key of Orders is (CustomerId, OrderId) where OrderId is a UUID. The primary key of OrderItems is (CustomerId, OrderId, ItemId). However, writes to OrderItems are creating hotspots. What is the most likely cause?

Accepted Answer

The leading key (CustomerId) is monotonically increasing. Hotspots occur when writes are concentrated on a small range of keys. Since OrderId is a UUID, it's already random. However, using CustomerId as the first part of the primary key can cause hotspots if certain customers place many orders. But more commonly, if OrderItems uses the same CustomerId and OrderId, and many items are inserted for the same order, they will be interleaved and written sequentially. Still, the hotspot is due to the leading key CustomerId being monotonically increasing if customers are assigned IDs sequentially. The best answer is that the primary key design leads to concentrated writes because CustomerId is not distributed well. However, the question likely expects that the primary key design is correct (UUID) but the hotspot might be due to not using a hash prefix. Actually, in Spanner, the first key part should be distributed. If CustomerId is sequential (e.g., auto-increment), it causes hotspots. So the cause is a monotonically increasing leading key. The correct answer should point to the leading key being monotonically increasing.

Answer

Using UUID for OrderId causes random writes

Answer

The primary key is too long

Answer

The parent-child interleaving is not defined correctly

Question 7

A retail company uses BigQuery to store sales data. The 'sales' table has 10 billion rows and is partitioned by transaction_date (daily). The BI dashboard runs a query that aggregates sales by product_category for the last 30 days. The query is slow and expensive. Which improvement is most effective?

Accepted Answer

Cluster the table on product_category. Clustering the table on product_category organizes the data within each daily partition by that column, allowing BigQuery to use block-level pruning to skip irrelevant blocks when filtering or aggregating by product_category. This directly reduces the amount of data scanned for the 30-day aggregation query, improving both performance and cost.

Answer

Change partitioning to monthly

Answer

Denormalize the product_category into the sales table

Answer

Use a materialized view with aggregation on product_category

Question 8

A logistics company uses BigQuery to track shipments. The `shipments` table has columns `id`, `status`, `created_date`, and `delivery_date`. They need a query that returns the number of shipments that were delivered within 5 days of creation for each month of 2024. Which SQL construct is most appropriate?

Accepted Answer

SELECT EXTRACT(MONTH FROM created_date) AS month, COUNT(*) FROM shipments WHERE DATETIME_DIFF(delivery_date, created_date, DAY) <= 5 AND EXTRACT(YEAR FROM created_date) = 2024 GROUP BY month. It uses `DATETIME_DIFF` with `DAY` precision to accurately compute the difference between `delivery_date` and `created_date` in days, and filters for shipments delivered within 5 days (i.e., <= 5 days). The `WHERE` clause also restricts to the year 2024, and the `GROUP BY month` with `EXTRACT(MONTH FROM created_date)` correctly aggregates counts per month. This matches the requirement precisely.

Answer

SELECT EXTRACT(MONTH FROM created_date) AS month, COUNT(*) FROM shipments WHERE TIMESTAMP_DIFF(delivery_date, created_date, HOUR) <= 120 AND EXTRACT(YEAR FROM created_date) = 2024 GROUP BY month

Answer

SELECT EXTRACT(MONTH FROM created_date) AS month, COUNTIF(DATETIME_DIFF(delivery_date, created_date, DAY) <= 5) FROM shipments WHERE EXTRACT(YEAR FROM created_date) = 2024 GROUP BY month

Answer

SELECT EXTRACT(MONTH FROM created_date) AS month, COUNT(*) FROM shipments WHERE DATE_DIFF(delivery_date, created_date, DAY) <= 5 AND EXTRACT(YEAR FROM created_date) = 2024 GROUP BY month

Question 9

An e-commerce site uses Cloud SQL for MySQL. They need read scalability for product catalog queries. What should they do?

Accepted Answer

Add read replicas. Adding read replicas in Cloud SQL for MySQL offloads read traffic from the primary instance, providing horizontal read scalability for product catalog queries. Replicas asynchronously replicate data using MySQL's native binary log replication, allowing the primary to focus on writes while replicas handle read-heavy workloads.

Answer

Partition tables

Answer

Use Cloud Spanner

Answer

Enable automatic storage increase

Question 10

A company needs to store session data for a web application that runs on Google Kubernetes Engine (GKE). The data is temporary and high-availability is required. Which database service is most appropriate?

Accepted Answer

Memorystore for Redis with replication. Memorystore for Redis with replication is the most appropriate choice because session data is temporary, requires high availability, and benefits from Redis's in-memory, low-latency key-value store. Replication provides failover capability, ensuring session continuity if a primary node fails, while Redis's built-in expiry (TTL) handles temporary data cleanup automatically.

Answer

Cloud Spanner

Answer

Cloud SQL for MySQL

Answer

Cloud Bigtable

Question 11

Which THREE actions can help reduce read latency in Cloud Spanner?

Accepted Answer

Use read-only transactions with strong consistency. Read-only transactions with strong consistency in Cloud Spanner use lock-free reads that return the most recent data without blocking writes. This reduces read latency because the system can serve the data directly from the current timestamp without waiting for write locks or replication delays, making it ideal for low-latency, strongly consistent reads.

Answer

Increase the staleness allowed for read queries

Answer

Batch multiple write operations into a single mutation

Question 12

An application running on GKE emits custom metrics via OpenTelemetry. The metrics need to be ingested into Cloud Monitoring and visualized in a dashboard. Which approach should the engineer use?

Accepted Answer

Install the OTel Collector as a DaemonSet and configure the Google Cloud Monitoring exporter.

Answer

Use the Cloud Monitoring API to directly ingest metrics from the application.

Answer

Configure the application to write logs in JSON format and create a log-based metric.

Answer

Use the Operations Agent on the node to scrape metrics from the application.

Question 13

Which Google Cloud service provides continuous, low-overhead profiling of CPU and memory usage to identify performance bottlenecks in production?

Accepted Answer

Cloud Profiler

Answer

Error Reporting

Answer

Cloud Monitoring

Answer

Cloud Trace

Question 14

A company uses Firestore in Native mode and has a collection with many documents containing array fields. They want to index the array values to support queries like 'array-contains'. What is the correct approach?

Accepted Answer

No additional index configuration is required; arrays are automatically indexed. In Firestore Native mode, all fields are automatically indexed by default, including array fields. For array fields, the index includes each element, which allows queries using the `array-contains` operator to work without any additional configuration. Index exemptions are used to exclude specific fields from automatic indexing, not to enable indexing. Therefore, no action is required.

Answer

Create an index exemption for the array field to enable indexing

Answer

Switch to Datastore mode and configure indexes manually

Answer

Create a composite index that includes the array field

Question 15

An SRE team is designing an incident management process. Which TWO components are part of a typical incident command structure?

Accepted Answer

Incident Commander. The incident command structure includes an Incident Commander (overall lead) and a Communications Lead (liaison for stakeholders). The SRE lead may be Incident Commander. Developer is a generic role; on-call engineer is a role but not part of the command structure per se.

Answer

Developer

Answer

On-call engineer

Answer

Product Manager

Question 16

An SRE team wants to track the amount of toil their team performs each week. According to SRE best practices, what is the recommended maximum percentage of time that should be spent on toil?

Accepted Answer

50%. Google SRE recommends that teams spend no more than 50% of their time on toil, leaving the rest for engineering work that reduces future toil or improves the service.

Answer

25%

Answer

10%

Answer

75%

Question 17

A company is using Cloud SQL for PostgreSQL and wants to improve read scalability for a reporting dashboard that executes complex aggregate queries. The reports can tolerate up to 5 minutes of data staleness. Which two actions should the team take?

Accepted Answer

Create read replicas in Cloud SQL and configure the reporting application to connect to the replicas. Creating read replicas in Cloud SQL offloads read traffic from the primary instance, allowing complex aggregate queries to run on replicas without impacting write performance. Since the reports can tolerate up to 5 minutes of staleness, the asynchronous replication lag inherent in Cloud SQL read replicas is acceptable, making this a cost-effective and scalable solution.

Answer

Enable PostgreSQL query cache to speed up aggregate queries

Answer

Increase the number of vCPUs on the primary instance to handle more queries

Answer

Configure a connection pool to reduce connection overhead

Question 18

A company collects sensor data from millions of devices globally. Each write is a small record with a device ID and timestamp. They need low write latency and high availability. Which database should they choose?

Accepted Answer

Cloud Bigtable. Cloud Bigtable is a fully managed, scalable NoSQL database designed for large analytical and operational workloads with high throughput and low latency. It supports millions of writes per second from globally distributed devices, provides high availability through replication, and is optimized for time-series data like sensor records with device IDs and timestamps.

Answer

Cloud Firestore

Answer

Cloud Memorystore

Answer

Cloud SQL for MySQL

Question 19

A company uses BigQuery BI Engine for sub-second query performance. However, some queries are hitting the BI Engine memory limit. Which action should be taken?

Accepted Answer

Increase BI Engine capacity allocation.. BI Engine is an in-memory analysis service that accelerates queries by caching data in memory. When queries exceed the allocated memory, they spill to disk, causing performance degradation. Increasing the BI Engine capacity allocation directly addresses this by providing more memory for caching, enabling sub-second query performance for larger datasets.

Answer

Cluster the tables more granularly.

Answer

Use a reservation with a higher slot count.

Answer

Optimize the dimension tables by denormalizing.

Question 20

A team is migrating to GCP and wants to use Cloud Deployment Manager for infrastructure. They have existing Terraform modules. What is the best approach?

Accepted Answer

Use Terraform with a GCS backend; avoid Deployment Manager.. The team already has existing Terraform modules, and using Terraform with a GCS backend allows them to continue leveraging their investment in Terraform without rewriting or bridging tools. Cloud Deployment Manager is a native Google Cloud IaC tool, but it does not natively import or execute Terraform configurations; forcing a migration or hybrid approach introduces unnecessary complexity and risk. The best practice is to standardize on one IaC tool, and since Terraform is already in use, using it with a GCS backend for state management is the most efficient and reliable path.

Answer

Use Deployment Manager only for new resources and Terraform for existing.

Answer

Convert Terraform modules to Deployment Manager templates manually.

Answer

Run Terraform as a subprocess within Deployment Manager.