PMLE Scaling Prototypes into ML Models Practice Test 4 — 15 Questions

Question 1

A data scientist has a TensorFlow 2.x model trained on a single GPU. They want to scale training to multiple GPUs on a single Vertex AI machine without code changes. Which strategy should they use?

Accepted Answer

MirroredStrategy. MirroredStrategy distributes training across GPUs on a single machine with minimal code changes — just wrap model creation and compile inside the strategy scope. MultiWorkerMirroredStrategy is for multi-machine, not single-machine multi-GPU.

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MultiWorkerMirroredStrategy

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TPUStrategy

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CentralStorageStrategy

Question 2

You are fine-tuning a BERT model from Hugging Face Transformers on Vertex AI. You want to minimise cost for a short experiment. Which compute configuration should you use?

Accepted Answer

A custom training job with a single NVIDIA T4 GPU using spot VMs. Spot VMs provide up to 60-90% discount compared to regular VMs. Since the experiment is short, preemption risk is low. Custom TPU pods are expensive and overkill; T4 GPUs are cheaper but spot VMs are the most cost-effective.

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A custom training job with a TPU v3-8 pod

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A custom training job with 8 NVIDIA V100 GPUs using regular VMs

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A standard n1-highmem-8 machine with no accelerator

Question 3

An ML engineer is using Vertex AI Vizier to tune hyperparameters for a PyTorch model. They want to maximise the chance of finding the global optimum within a fixed trial budget of 50 trials. Which algorithm should they select?

Accepted Answer

Bayesian optimisation. Bayesian optimisation (option B) is the correct choice because it builds a probabilistic surrogate model of the objective function and uses an acquisition function to balance exploration and exploitation, making it highly sample-efficient. With only 50 trials, Bayesian optimisation maximises the probability of finding the global optimum by focusing trials on the most promising hyperparameter regions, unlike random or grid search which waste trials on unpromising areas.

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Random search

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Grid search

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Evolutionary algorithm

Question 4

Your team is deploying a large language model (LLM) on Vertex AI for online prediction. The model exceeds the maximum request size for Vertex AI Prediction. Which approach should you take to serve this model?

Accepted Answer

Deploy the model on a Compute Engine VM with a custom container and a load balancer. Vertex AI Prediction has a request size limit (1.5 MB). Using a custom container with a ModelServer (e.g., TensorFlow Serving) behind an HTTP load balancer bypasses this limit and allows large payloads.

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Use Vertex AI Endpoint with a larger machine type and gRPC

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Use Vertex AI Batch Prediction

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Split the model into smaller parts and deploy multiple endpoints

Question 5

You are using TensorFlow Transform (tf.Transform) to preprocess data for a model that will be deployed on Vertex AI. What is the primary benefit of using tf.Transform over Dataflow alone?

Accepted Answer

Training/serving skew prevention through a consistent transformation graph. tf.Transform computes statistics (e.g., min, max) on the full dataset, then generates a TensorFlow graph that applies the same transformation consistently at training and serving time. Dataflow alone does not ensure this consistency.

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Support for GPUs during preprocessing

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Built-in feature store integration

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Faster data processing

Question 6

An ML engineer wants to use Vertex AI Model Garden to deploy a pre-trained foundation model for text summarisation. What is the quickest way to achieve this?

Accepted Answer

Use Vertex AI JumpStart to deploy the model with one click. Vertex AI JumpStart provides one-click deployment of foundation models like Llama, Gemini, etc. Model Garden is for discovery, but JumpStart directly deploys.

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Use Vertex AI AutoML for text summarisation

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Use Vertex AI Pipelines to build a custom training pipeline

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Export the model from Model Garden and deploy using a custom container

Question 7

Your team is training a very large transformer model that does not fit on a single GPU. They are using Vertex AI custom training with PyTorch. Which distributed training approach should they use?

Accepted Answer

Model parallelism using pipeline parallelism. When a transformer model is too large to fit on a single GPU, model parallelism (specifically pipeline parallelism) is required because it splits the model's layers across multiple devices, with each device holding a subset of the model's parameters. Data parallelism (DDP) replicates the entire model on each GPU, which fails if the model exceeds a single GPU's memory. Pipeline parallelism allows training very large models by partitioning the model into stages and passing activations and gradients sequentially between devices.

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Data parallelism using PyTorch DistributedDataParallel (DDP)

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Horovod with allreduce

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Vertex AI distributed training with TF_CONFIG

Question 8

You are performing post-training quantisation of a trained TensorFlow model to INT8 for deployment on edge devices. Which technique should you use to minimise accuracy loss?

Accepted Answer

Quantisation-aware training. Quantisation-aware training (QAT) simulates quantisation during training, allowing the model to adapt, resulting in higher accuracy than post-training quantisation. Post-training quantisation is simpler but may lose accuracy.

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Float16 quantisation

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Post-training integer quantisation with calibration

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Post-training dynamic range quantisation

Question 9

An ML team is building a feature pipeline with Dataflow that reads from BigQuery, computes features, and writes to Vertex AI Feature Store. They need to ensure that features are available for both training and serving with low latency. Which Feature Store option should they use?

Accepted Answer

Create a featurestore with online serving enabled. Vertex AI Feature Store supports online serving (low latency) and offline serving (batch). For low latency, they must enable online serving. The online store uses Bigtable for low-latency lookups.

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Create a featurestore with only offline serving

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Store features directly in BigQuery

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Use Cloud SQL as a feature store

Question 10

You need to run a custom training job on Vertex AI using a pre-built container for scikit-learn. Which container image should you specify?

Accepted Answer

us-docker.pkg.dev/vertex-ai/training/scikit-learn-cpu.0.23-0. Vertex AI provides pre-built containers for scikit-learn with the prefix 'us-docker.pkg.dev/vertex-ai/training/scikit-learn-cpu.0.23-0'. The others are for different frameworks.

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us-docker.pkg.dev/vertex-ai/training/pytorch-gpu.1-9

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us-docker.pkg.dev/vertex-ai/training/xgboost-cpu.1-3

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us-docker.pkg.dev/vertex-ai/training/tf-cpu.2-6

Question 11

You are fine-tuning a pre-trained model using transfer learning. The new dataset is small and very similar to the original training data. To avoid overfitting, which layer freezing strategy should you adopt?

Accepted Answer

Freeze all layers and train only the classifier head. When fine-tuning a pre-trained model on a small dataset that is very similar to the original training data, the safest strategy to avoid overfitting is to freeze all layers and train only the classifier head. This preserves the rich, general-purpose feature representations learned from the original large dataset, while allowing the final classification layer to adapt to the new task. Training the entire model or unfreezing many layers on a small dataset would risk overfitting because the model would have too many parameters to update relative to the limited new samples.

Answer

Unfreeze the last few layers and freeze the rest

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Randomly reinitialise all layers and train from scratch

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Unfreeze all layers and train the entire model

Question 12

You are using Vertex AI hyperparameter tuning with a custom container. The training job reports the objective metric but Vizier is not converging. Which configuration change could improve convergence?

Accepted Answer

Increase the number of parallel trials. Increasing the number of parallel trials can help explore more of the hyperparameter space, but the specified number of max trials must be high enough. Reducing parallel trials may slow exploration. Bayesian optimisation benefits from more trials.

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Use a larger machine type for each trial

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Reduce the number of parallel trials

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Switch from Bayesian to grid search

Question 13

You are designing a distributed training job for a PyTorch model on Vertex AI using multiple machines with GPUs. Which TWO configurations are required to enable data parallelism with PyTorch DDP? (Choose 2.)

Accepted Answer

Use the command 'torch.distributed.launch' to start each worker.. PyTorch DDP requires the master address and port (MASTER_ADDR, MASTER_PORT) for the communication group, and WORLD_SIZE and RANK. Vertex AI sets TF_CONFIG for TensorFlow, not PyTorch. NCCL is the backend.

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Enable Vertex Explainable AI during training.

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Set environment variable TF_CONFIG for each replica.

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Specify a custom service account with access to Cloud TPU.

Question 14

Your team is deploying a large model on edge devices and needs to reduce its size by 80% while maintaining reasonable accuracy. Which THREE techniques should they consider? (Choose 3.)

Accepted Answer

Quantisation to INT8. Quantisation to INT8 reduces the precision of model weights and activations from 32-bit floating point to 8-bit integers, cutting memory usage by approximately 75% (4x compression). This directly addresses the 80% size reduction target while often preserving accuracy within 1-2% through careful calibration and scaling, making it a primary technique for edge deployment.

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Transfer learning from a larger model

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Increasing model capacity with more layers

Question 15

You are using Vertex AI to train a model with a custom container. You need to pass command-line arguments for hyperparameters. Which TWO methods can you use? (Choose 2.)

Accepted Answer

Set environment variables using the 'env' field and reference them in the container.. Option B is correct because Vertex AI custom container training allows you to pass environment variables via the 'env' field in the worker pool spec, which the container can then reference at runtime. Option D is correct because you can override the container's default entrypoint using the 'command' field and include command-line arguments directly in that field. Option E is also correct as the 'args' field in the container spec can be used to pass arguments that are appended to the entrypoint or command.

Answer

Store arguments in a Cloud Storage file and download at runtime.

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Set hyperparameter values in the 'hyperparameters' field of the worker pool spec.