The correct answer is to use AWS Lambda functions triggered by S3 events to run the transformation, then invoke a SageMaker endpoint. This works because S3 object creation events can directly trigger a Lambda function, which executes your custom Python script serverlessly, and the transformed output is then passed to a SageMaker real-time endpoint for inference—creating a fully event-driven, serverless real-time inference pipeline with S3 and Lambda. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this question tests your ability to distinguish between serverless compute (Lambda) and managed compute (SageMaker Processing, which runs on EC2 and is not serverless). A common trap is choosing Glue (designed for batch ETL, not real-time) or Kinesis Data Firehose (for streaming ingestion, not S3-triggered events). Memory tip: think "S3 event → Lambda transform → SageMaker predict" as the serverless inference chain.
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 machine learning team is building a real-time inference pipeline using Amazon SageMaker. The input data is located in an S3 bucket, and the team needs to transform the data before inference using a custom Python script. The transformation should run on a serverless infrastructure and must be triggered automatically when new data arrives in S3. Which combination of services should the team use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Lambda functions triggered by S3 events to run the transformation, then invoke a SageMaker endpoint.
Option C is correct because S3 events can trigger Lambda, which runs the custom script, and the output can be sent to a SageMaker endpoint for inference. Option A is wrong because SageMaker Processing is not serverless (it runs on EC2 instances). Option B is wrong because Glue is for ETL, not real-time inference. Option D is wrong because Kinesis Data Firehose is for streaming ingestion, not suitable for S3-triggered batch processing.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Use AWS Lambda functions triggered by S3 events to run the transformation, then invoke a SageMaker endpoint.
Why this is correct
Lambda provides serverless compute triggered by S3 events, and can call SageMaker endpoints.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use AWS Glue jobs triggered by S3 events.
Why it's wrong here
Glue is designed for ETL, not real-time inference pipelines.
✗
Use Amazon SageMaker Processing jobs triggered by S3 events.
Why it's wrong here
SageMaker Processing jobs run on provisioned instances, not serverless.
✗
Use Amazon Kinesis Data Firehose to transform data and deliver to SageMaker.
Why it's wrong here
Firehose is for streaming data, not suitable for S3-triggered processing.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related MLS-C01 NAT questions on configuration and troubleshooting.
Data Engineering — This question tests Data Engineering — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use AWS Lambda functions triggered by S3 events to run the transformation, then invoke a SageMaker endpoint. — Option C is correct because S3 events can trigger Lambda, which runs the custom script, and the output can be sent to a SageMaker endpoint for inference. Option A is wrong because SageMaker Processing is not serverless (it runs on EC2 instances). Option B is wrong because Glue is for ETL, not real-time inference. Option D is wrong because Kinesis Data Firehose is for streaming ingestion, not suitable for S3-triggered batch processing.
What should I do if I get this MLS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related MLS-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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