The answer is that the endpoint has multiple variants and the old variant still has a weight assigned. This occurs because when you update a SageMaker endpoint with a new configuration, you can add or modify production variants, each with a traffic weight; if the old variant’s weight is not set to zero, it continues to receive a portion of the requests, serving outdated predictions. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding of SageMaker endpoint routing and production variant weights, often appearing as a trick where candidates assume a new endpoint configuration automatically replaces all traffic. A common trap is overlooking that weights persist across updates unless explicitly adjusted. Memory tip: think of it like a dimmer switch—turning down the old variant’s weight to zero is the only way to fully cut its power.
MLS-C01 Practice Question: Machine Learning Implementation and Operations
This MLS-C01 practice question tests your understanding of machine learning implementation and operations. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has a SageMaker endpoint that serves predictions for a mobile app. The endpoint is deployed on a single ml.m5.large instance. Recently, users have reported that the app sometimes returns outdated predictions. The data science team has confirmed that the model is updated daily by retraining with new data and creating a new endpoint configuration. However, the endpoint still returns predictions from the old model for some requests. The team has verified that the new endpoint configuration is associated with the endpoint and that the endpoint is in service. What is the most likely cause of this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The old model artifacts are still being cached by the endpoint
Why wrong: Model artifacts are not cached; the endpoint loads the model from S3.
B
The endpoint has multiple variants and the old variant still has a weight assigned
If the old variant has a weight, it will continue to serve traffic. The new variant should get a weight of 1 and the old variant weight should be set to 0.
C
The mobile app is using a CDN that caches the predictions
Why wrong: The CDN issue is possible but less likely than a variant weight issue.
D
The new endpoint configuration has not been deployed to the endpoint
Why wrong: The team verified that the new configuration is associated and the endpoint is in service.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The endpoint has multiple variants and the old variant still has a weight assigned
Option D is correct because if the old endpoint variant still has a weight greater than zero, some traffic will continue to be routed to the old model. Option A is wrong because if the new configuration were not active, the endpoint would not be in service. Option B is wrong because the model artifacts are stored in S3 and are not deleted during updates. Option C is wrong because CloudFront does not cache SageMaker endpoint responses by default.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The old model artifacts are still being cached by the endpoint
Why it's wrong here
Model artifacts are not cached; the endpoint loads the model from S3.
✓
The endpoint has multiple variants and the old variant still has a weight assigned
Why this is correct
If the old variant has a weight, it will continue to serve traffic. The new variant should get a weight of 1 and the old variant weight should be set to 0.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The mobile app is using a CDN that caches the predictions
Why it's wrong here
The CDN issue is possible but less likely than a variant weight issue.
✗
The new endpoint configuration has not been deployed to the endpoint
Why it's wrong here
The team verified that the new configuration is associated and the endpoint is in service.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Machine Learning Implementation and Operations — This question tests Machine Learning Implementation and Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The endpoint has multiple variants and the old variant still has a weight assigned — Option D is correct because if the old endpoint variant still has a weight greater than zero, some traffic will continue to be routed to the old model. Option A is wrong because if the new configuration were not active, the endpoint would not be in service. Option B is wrong because the model artifacts are stored in S3 and are not deleted during updates. Option C is wrong because CloudFront does not cache SageMaker endpoint responses by default.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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