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Inference cost and capacity: MLA-C02 study notes and practice questions

What to know about Inference cost and capacity for the MLA-C02 exam, from the Operating, Monitoring, and Securing ML and AI Solutions domain (24% of the exam guide), then 2 free questions to test it. Part of the MLA-C02 study guide.

Last verified against current AWS documentation ·How we write our questions

What to know for the exam

Cost questions give a workload and ask for the biggest saving that still meets requirements.

Training

  • Managed Spot training with checkpoints for restartable jobs.
  • Right-size instances; many classic algorithms don’t need GPUs.
  • Fast File mode or FSx for Lustre so expensive GPUs don’t wait on data.
  • Trainium instances for lower-cost deep learning training.
  • Stop idle notebooks and Studio apps (lifecycle configurations can shut them down automatically).

Hosting

Lever Saves when
SageMaker Savings Plans Steady, year-round usage; commit to an hourly spend for one or three years
Serverless inference Traffic is intermittent; no paying for idle time
Asynchronous inference Can scale to zero between bursts of large jobs
Batch transform Predictions are needed offline
Multi-model endpoints / inference components Many models share instances
Auto scaling Traffic varies during the day
Inference Recommender Load tests find the cheapest instance that meets latency
AWS Inferentia with SageMaker Neo or the Neuron SDK Compiled models run at lower cost per inference
Graviton CPU instances CPU inference

Compute Savings Plans don’t cover SageMaker AI; use SageMaker Savings Plans.

Bedrock

  • Choose the smallest model that meets quality; use distillation or intelligent prompt routing.
  • Batch inference at a discount for non-urgent jobs.
  • Prompt caching for repeated context.
  • Cap max tokens and keep prompts lean.
  • Provisioned throughput only for steady high volume.

Tracking

  • Cost allocation tags on jobs and endpoints; AWS Budgets alerts; Cost Explorer by service and tag.

Common traps

  • A larger GPU to cut cost.
  • Scaling to zero a service with steady traffic and strict latency.
  • Compute Savings Plans expected to cover SageMaker AI.

Try the 2 practice questions

A dental chain serves an X-ray triage image model on GPU instances in SageMaker AI. Traffic is steady, and the model is a standard convolutional network trained and validated in TensorFlow. The finance team wants the inference cost cut without rewriting the model.

Inference latency must stay within the current service target, and the team is willing to compile the model for new target hardware as a one-time step.

Which change best meets these requirements?

Choose one answer.

  1. A. Move the endpoint to a larger GPU instance type, so that each request finishes sooner and the endpoint is billed for fewer instance hours.
  2. B. Replace the model with a rule-based image threshold that requires no model at all, since rules never cost money to serve.
  3. C. Turn off all logging and monitoring on the endpoint, which removes the cost of the logs without changing the model.
  4. D. Compile the model with SageMaker Neo for an AWS Inferentia instance type, and deploy the compiled model to an Inferentia-based endpoint that meets the latency target.
Show the answer and explanation

Answer: D

  • A. Wrong: A larger instance costs more per hour, and the total hours do not necessarily fall for a steady workload. The option raises cost rather than cutting it.
  • B. Wrong: Rules may not match the accuracy of the model for X-ray triage, and the stem asks to keep the model without rewriting it. The option changes the service.
  • C. Wrong: Logging is a small share of the cost, and removing monitoring weakens the operations the team relies on. The option does not address the instance cost that drives the bill.
  • D. Right: Correct. Inferentia instances offer lower inference cost for supported models, and SageMaker Neo compiles a validated model for that hardware. The one-time compile step matches the team's willingness to do it. Learn more: Model performance optimization with SageMaker Neo (opens in a new tab)

Explanation

Inferentia instances provide lower-cost inference for models that compile for them, and SageMaker Neo compiles a validated model for that hardware in one step. A larger GPU, a rule-based replacement or turning off monitoring each raise cost, change the service or weaken operations.

Study

Question 2

Medium · choose 2 ·Link to this question (question 2)

A solar installer runs two kinds of ML workloads on AWS. Nightly model training jobs run for about four hours each and can be restarted if interrupted. A real-time forecasting endpoint runs all day at a steady load on the same instance type for the whole year.

The finance team wants lower cost for both workloads without changing the models, the instance families they are built for, or the forecasting service targets.

Which TWO actions meet these requirements? (Choose two.)

Choose two answers.

  1. A. Use managed Spot training for the nightly jobs, with checkpoints saved to Amazon S3 so that an interrupted job resumes.
  2. B. Purchase a SageMaker AI Savings Plan for the steady, all-year inference usage, so the hourly rate for the endpoint is lower.
  3. C. Move the nightly jobs to On-Demand capacity with larger instance types, so that each job finishes in one hour and costs less overall.
  4. D. Reduce the endpoint's minimum instance count to zero during the day, so the endpoint stops running when traffic is low.
  5. E. Turn off the training jobs entirely and use the previous quarter's model for all forecasts, which removes the training cost.
Show the answer and explanation

Answers: A, B

  • A. Right: Correct. Managed Spot training uses discounted capacity for the restartable nightly jobs, and checkpoints let an interrupted job resume. The models and instance family stay the same. Learn more: Managed Spot Training in Amazon SageMaker AI (opens in a new tab)
  • B. Right: Correct. Savings Plans give a lower rate in exchange for a steady commitment, which fits an endpoint that runs all year on the same type. The endpoint and its instance type do not change. Learn more: What are Savings Plans? (opens in a new tab)
  • C. Wrong: Larger On-Demand instances cost more per hour, and the stem asks for lower cost. The option pays more for the same training work.
  • D. Wrong: The stem describes steady traffic all day, so scaling to zero would break the forecasting service targets. The option conflicts with the stated requirement.
  • E. Wrong: The stem requires the models to keep their current training. Skipping retraining would also let the forecasts drift, which the team does not want.

Explanation

Managed Spot training with checkpoints lowers the cost of restartable nightly training, and a Savings Plan lowers the rate for steady, all-year endpoint usage. Larger On-Demand instances, scaling to zero during steady traffic and skipping retraining each raise cost or break a stated requirement.

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