PCDE Optimising Service Performance Practice Test 3 — 15 Questions

Question 1

A DevOps team has a GKE workload that experiences fluctuating traffic. They want to automatically adjust the number of pods based on CPU utilization. Which resource should they configure?

Accepted Answer

Horizontal Pod Autoscaler. Horizontal Pod Autoscaler (HPA) automatically scales the number of pod replicas based on observed CPU utilization or other metrics, which is exactly what the team needs.

Answer

Pod Disruption Budget

Answer

Vertical Pod Autoscaler

Answer

Cluster Autoscaler

Question 2

A team uses Cloud Run for a web application that experiences sporadic traffic. They want to minimize cold starts without incurring costs when there are no requests. Which configuration should they use?

Accepted Answer

Set min instances to 0. Min instances set to 0 allows the service to scale to zero when idle, eliminating cost. To reduce cold starts, they can also adjust concurrency and CPU, but min instances=0 is the key for cost savings.

Answer

Set min instances to a value greater than 0

Answer

Set CPU always-on to true

Answer

Set concurrency to 1000

Question 3

A Cloud Spanner database uses a sequential customer ID as the primary key, causing frequent hotspotting on a single split. The team needs to eliminate hotspots. Which key design should they implement?

Accepted Answer

Add a hash prefix derived from the customer ID. Hotspots occur with monotonically increasing keys. Using a hash prefix or UUID spreads writes across splits. Bit-reverse is another technique for integers. The simplest is to add a hash prefix to the key.

Answer

Use a composite key with a monotonically increasing timestamp as the first part

Answer

Use a random UUID as the primary key

Answer

Keep the sequential key but add a secondary index

Question 4

An application running on Cloud SQL experiences high read latency. The team wants to offload read traffic from the primary instance and improve performance. Which approach should they take?

Accepted Answer

Create a single read replica and route read-only queries to it. Cloud SQL read replicas allow distributing read traffic, reducing load on the primary instance and improving read performance.

Answer

Add more memory to the primary instance

Answer

Enable the query cache

Answer

Use Cloud SQL Auth Proxy

Question 5

A team wants to automatically adjust the node count in a GKE cluster based on pending pod resource requests. Which component should they enable?

Accepted Answer

Cluster Autoscaler. The Cluster Autoscaler automatically adds or removes nodes from the cluster based on pending pods or underutilized nodes.

Answer

Vertical Pod Autoscaler

Answer

Node auto-provisioning

Answer

Horizontal Pod Autoscaler

Question 6

A Pub/Sub subscription is processing messages but the subscriber cannot keep up. The team notices that many messages are being resent. Which parameter should they adjust to reduce duplicate processing?

Accepted Answer

Increase the acknowledgement deadline. Increasing the acknowledgement deadline gives the subscriber more time to process and ack messages, reducing the chance that they expire and are redelivered.

Answer

Decrease the acknowledgement deadline

Answer

Increase the retention duration

Answer

Enable ordering keys

Question 7

A DevOps engineer is setting up a GKE cluster for a batch processing job that can tolerate interruptions. The job runs for a few hours daily. To optimize cost, they want to use preemptible VMs. What must they configure to ensure the job completes despite node preemptions?

Accepted Answer

Set the cluster autoscaler min nodes low and max nodes high to allow replacement. To ensure the batch job completes despite node preemptions, the cluster autoscaler must be able to replace preempted nodes. Option D sets the minimum nodes low (to avoid unnecessary cost) and maximum nodes high (to allow scaling up when nodes are preempted). This allows the autoscaler to launch new preemptible nodes as replacements. The job itself must be fault-tolerant and handle restarts, but the autoscaler configuration is what enables node replacement. Option A disables autoscaling, preventing replacement. Option B is unrelated to node replacement. Option C prevents scaling, so preempted nodes cannot be replaced.

Answer

Disable cluster autoscaler to avoid node churn

Answer

Use a stateful workload with persistent volumes

Answer

Set the cluster autoscaler min and max nodes to the same value

Question 8

A Cloud Run service needs to handle background tasks after responding to a client. Which CPU configuration is required to ensure background tasks complete?

Accepted Answer

CPU always-on: true. CPU always-on must be enabled for Cloud Run to run background tasks; otherwise, CPU is throttled after the request is handled.

Answer

Set concurrency to 1

Answer

CPU always-on: false (default)

Answer

Set execution environment to gen1

Question 9

A Cloud Spanner query is performing a join between two tables that are frequently accessed together. Which schema design can optimize this query?

Accepted Answer

Use interleaved tables. Interleaved tables store child rows physically with parent rows, improving locality for parent-child joins.

Answer

Use a foreign key constraint

Answer

Create a secondary index

Answer

Denormalize the data into a single table

Question 10

A team has a Cloud SQL instance with high CPU usage from many concurrent connections. They want to reduce connection overhead and improve performance. Which combination of services should they implement?

Accepted Answer

Cloud SQL Auth Proxy with PgBouncer. Cloud SQL Auth Proxy provides secure connections, and PgBouncer (connection pooler) manages a pool of connections to reduce overhead.

Answer

Use a network proxy like HAProxy

Answer

Cloud SQL Proxy with read replicas

Answer

Vertical scaling by increasing vCPU

Question 11

A batch job on GKE needs to be resilient to node failures. The job creates several pods that run for a few minutes each. The team wants to ensure that during a voluntary node disruption (e.g., node upgrade), only a limited number of pods are affected. Which resource should they configure?

Accepted Answer

Pod Disruption Budget. PodDisruptionBudget (PDB) specifies the minimum number of pods that must remain available during voluntary disruptions, protecting the job.

Answer

Vertical Pod Autoscaler

Answer

Horizontal Pod Autoscaler

Answer

Cluster Autoscaler

Question 12

A team is using Cloud Spanner and wants to reduce latency for queries that filter on a column that is not part of the primary key. Which feature should they use?

Accepted Answer

Secondary index. Secondary indexes allow efficient queries on non-primary-key columns.

Answer

Storing index

Answer

Interleaved table

Answer

Query explain plan

Question 13

A company runs a high-throughput pub/sub system. They need to improve message processing throughput. Which two actions should they take? (Choose TWO).

Accepted Answer

Increase the number of parallel pull subscribers. Increasing parallel pull consumers and enabling flow control can improve throughput by distributing load and preventing subscriber overload.

Answer

Enable ordering keys

Answer

Decrease the acknowledgement deadline

Answer

Use a single pull subscriber

Question 14

A DevOps engineer is optimizing a GKE workload that is CPU-bound. They want to ensure proper resource allocation to improve performance. Which three actions should they take? (Choose THREE).

Accepted Answer

Set Horizontal Pod Autoscaler based on CPU utilization. VPA recommends resource requests/limits; cluster autoscaler ensures node capacity; HPA handles scaling based on CPU.

Answer

Set min instances on Cloud Run

Answer

Use preemptible nodes

Question 15

A Cloud Spanner database is experiencing read performance issues. The team wants to optimize query performance. Which two approaches should they use? (Choose TWO).

Accepted Answer

Create secondary indexes on frequently filtered columns. Using query explain plan helps identify bottlenecks; secondary indexes speed up lookups.

Answer

Enable read replicas

Answer

Use interleaved tables for all tables

Answer

Increase the number of nodes