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PROFESSIONAL-MACHINE-LEARNING-ENGINEER · Question #249

You have deployed a scikit-team model to a Vertex AI endpoint using a custom model server. You enabled autoscaling: however, the deployed model fails to scale beyond one replica, which led to…

The correct answer is B. Increase the number of workers in your model server. If a custom model server with low CPU utilization fails to scale beyond one replica, the bottleneck is likely within the single replica's processing, meaning increasing internal workers in the model server will allow it to handle more concurrent requests.

Submitted by amina.ke· Apr 18, 2026Monitoring, optimizing, and maintaining ML solutions

Question

You have deployed a scikit-team model to a Vertex AI endpoint using a custom model server. You enabled autoscaling: however, the deployed model fails to scale beyond one replica, which led to dropped requests. You notice that CPU utilization remains low even during periods of high load. What should you do?

Options

  • AAttach a GPU to the prediction nodes
  • BIncrease the number of workers in your model server
  • CSchedule scaling of the nodes to match expected demand
  • DIncrease the minReplicaCount in your DeployedModel configuration

How the community answered

(16 responses)
  • A
    6% (1)
  • B
    81% (13)
  • D
    13% (2)

Why each option

If a custom model server with low CPU utilization fails to scale beyond one replica, the bottleneck is likely within the single replica's processing, meaning increasing internal workers in the model server will allow it to handle more concurrent requests.

AAttach a GPU to the prediction nodes

Attaching a GPU is for models that benefit from GPU acceleration, but the problem states CPU utilization is low, suggesting the bottleneck is not computational throughput but concurrency within the existing CPU capacity.

BIncrease the number of workers in your model serverCorrect

If CPU utilization is low but requests are dropped and scaling is stuck at one replica, the bottleneck is likely within the single model server process, meaning it can't handle more concurrent requests effectively. Increasing the number of workers *within* your custom model server allows the single replica to process more requests concurrently, effectively utilizing the available CPU and potentially resolving the bottleneck without needing more replicas.

CSchedule scaling of the nodes to match expected demand

Scheduling scaling might address predictable load, but it doesn't solve the underlying issue of why autoscaling *failed* to scale beyond one replica despite high load and low CPU utilization, which points to a bottleneck within the single replica's processing.

DIncrease the minReplicaCount in your DeployedModel configuration

Increasing `minReplicaCount` forces more replicas, which might provide more capacity, but it doesn't address the root cause of why the single replica isn't fully utilized or why autoscaling isn't working as expected.

Concept tested: Custom model server autoscaling and performance tuning

Source: https://cloud.google.com/vertex-ai/docs/predictions/troubleshoot-prediction

Topics

#Vertex AI#Custom Model Server#Autoscaling#Performance Optimization

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