Amazon Web Services Data-Engineer-Associate - AWS Certified Data Engineer - Associate (DEA-C01)

Apache Iceberg query performance depends heavily on metadata optimization and file layout efficiency. Generating column-level statistics allows query engines such as AWS Glue, Amazon Athena, and Amazon Redshift to perform predicate pushdown and data skipping. These statistics help avoid scanning unnecessary Parquet files and significantly reduce query execution time.

Real-time streaming workloads often generate many small files, which degrades query performance. Table compaction consolidates small Parquet files into fewer, larger files, improving scan efficiency and reducing metadata overhead. Iceberg supports compaction as a core optimization technique, and Glue can schedule these operations automatically.

Iceberg does not use traditional indexes, so index optimization is not applicable. Copy-on-write affects write semantics and consistency, not query speed. Views do not improve physical query performance.

Therefore, generating statistics and compacting files are the two most effective optimizations.

A sort-merge join generates large shuffle files, leading to “No space left on device” errors when both datasets are large. Using a broadcast join sends a smaller dataset to all executors, avoiding shuffle and disk I/O overhead.

“Broadcast joins reduce shuffle I/O by distributing the smaller dataset to all worker nodes, mitigating disk space and shuffle errors.”

– Ace the AWS Certified Data Engineer - Associate Certification - version 2 - apple.pdf

This is the most cost-effective and direct fix for large shuffle-stage failures.

The correct answer is B because AWS Glue streaming ETL jobs are built to continuously consume data from streaming sources such as Amazon Kinesis Data Streams, transform the data, and load the results into Amazon S3 data lakes. The requirement is not just delivery to S3; the telemetry JSON must be flattened before storage, and this needs to happen with low latency. Amazon Data Firehose can deliver streaming data, but the option incorrectly assumes automatic flattening without a transformation layer. SQS plus scheduled batch Glue introduces batch delay and does not meet the lowest-latency requirement. Athena is a query engine, not a real-time transformation and ingestion service for writing flattened streaming output to S3. AWS Glue streaming ETL is the correct serverless streaming transformation layer.

The correct answer is A because the pipeline requires scalable ingestion, PII removal, ETL transformation, centralized storage, and automatic retry handling. Amazon S3 is the correct landing and central storage layer for large hospital data files. AWS Glue ETL is appropriate for managed data transformation at this scale, and AWS Glue DataBrew is the best fit among the options for low-code data preparation and PII handling. Step Functions is the correct orchestration service because it supports retry policies for task states, parallel states, and map states without manual intervention. EC2 custom scripts and AWS Batch add more operational work. Lambda is not suitable for 5 GB per hospital with heavier transformation steps. Therefore, S3, Glue, DataBrew, and Step Functions is the least-operational-overhead design.

 The Amazon Redshift Data API is a built-in feature that allows you to run SQL queries on Amazon Redshift data with web services-based applications, such as AWS Lambda, Amazon SageMaker notebooks, and AWS Cloud9. The Data API does not require a persistent connection to your database, and it provides a secure HTTP endpoint and integration with AWS SDKs. You can use the endpoint to run SQL statements without managing connections. The Data API also supports both Amazon Redshift provisioned clusters and Redshift Serverless workgroups. The Data API is the best solution for running real-time queries on the financial data from within the trading application, as it has the least operational overhead compared to the other options.

Option A is not the best solution, as establishing WebSocket connections to Amazon Redshift would require more configuration and maintenance than using the Data API. WebSocket connections are also not supported by Amazon Redshift clusters or serverless workgroups.

Option C is not the best solution, as setting up JDBC connections to Amazon Redshift would also require more configuration and maintenance than using the Data API. JDBC connections are also not supported by Redshift Serverless workgroups.

Option D is not the best solution, as storing frequently accessed data in Amazon S3 and using Amazon S3 Select to run the queries would introduce additional latency and complexity than using the Data API. Amazon S3 Select is also not optimized for real-time queries, as it scans the entire object before returning the results. References:

Using the Amazon Redshift Data API

Calling the Data API

Amazon Redshift Data API Reference

AWS Certified Data Engineer - Associate DEA-C01 Complete Study Guide

Athena data source is a solution that allows you to use Spark to access Athena by using the Athena JDBC driver and the Spark SQL interface. You can use the Athena data source to create Spark DataFrames from Athena tables, run SQL queries on the DataFrames, and write the results back to Athena. The Athena data source supports various data formats, such as CSV, JSON, ORC, and Parquet, and also supports partitioned and bucketed tables. The Athena data source is a cost-effective and scalable way to use Spark to access Athena, as it does not require any additional infrastructure or services, and you only pay for the data scanned by Athena.

The other options are not solutions that give the company the ability to use Spark to access Athena. Option A, Athena query settings, is a feature that allows you to configure various parameters for your Athena queries, such as the output location, the encryption settings, the query timeout, and the workgroup. Option B, Athena workgroup, is a feature that allows you to isolate and manage your Athena queries and resources, such as the query history, the query notifications, the query concurrency, and the query cost. Option D, Athena query editor, is a feature that allows you to write and run SQL queries on Athena using the web console or the API. None of these options enable you to use Spark instead of SQL to generate analytics on Athena. References:

Using Apache Spark in Amazon Athena

Athena JDBC Driver

Spark SQL

Athena query settings

[Athena workgroups]

[Athena query editor]

Option B is the right approach because the requirement is to mask PII in the log destination (the CloudWatch Logs log group). The exam guide explicitly calls out security responsibilities that include “data encryption and masking” and also emphasizes enabling and preparing logs for audit and governance needs. A log-group–level masking mechanism is therefore the most direct control point to prevent sensitive values from being exposed to anyone who can view logs.

Option A (Glue security configuration) is primarily used to apply protections such as encryption settings for Glue jobs and related outputs; it does not inherently solve the problem of masking PII that has already been emitted into application logs. Option C (Macie) is intended to discover and classify sensitive data—most commonly in Amazon S3—and to produce findings; it is not a log-masking control for CloudWatch Logs. The material reinforces Macie as a discovery/classification service for PII rather than a masking mechanism. Option D adds custom code paths in the ETL job and still may miss PII that appears in framework/system logs; it also violates the “least operational effort” spirit compared to applying a centralized log policy.

Therefore, attaching a data protection policy directly to the CloudWatch Logs log group best meets the masking requirement.

AWS Glue workflows are a feature of AWS Glue that enable you to create and visualize complex ETL pipelines using AWS Glue components, such as crawlers, jobs, triggers, and development endpoints. AWS Glue workflows provide automated orchestration and require minimal manual effort, as they handle dependency resolution, error handling, state management, and resource allocation for your ETL workflows. You can use AWS Glue workflows to ingest data from your operational databases into your Amazon S3 based data lake, and then use AWS Glue and Amazon EMR to process the data in the data lake. This solution will meet the requirements with the least operational overhead, as it leverages the serverless and fully managed nature of AWS Glue, and the scalability and flexibility of Amazon EMR12.

The other options are not optimal for the following reasons:

B. AWS Step Functions tasks. AWS Step Functions is a service that lets you coordinate multiple AWS services into serverless workflows. You can use AWS Step Functions tasks to invoke AWS Glue and Amazon EMR jobs as part of your ETL workflows, and use AWS Step Functions state machines to define the logic and flow of your workflows. However, this option would require more manual effort than AWS Glue workflows, as you would need to write JSON code to define your state machines, handle errors and retries, and monitor the execution history and status of your workflows3.

C. AWS Lambda functions. AWS Lambda is a service that lets you run code without provisioning or managing servers. You can use AWS Lambda functions to trigger AWS Glue and Amazon EMR jobs as part of your ETL workflows, and use AWS Lambda event sources and destinations to orchestrate the flow of your workflows. However, this option would also require more manual effort than AWS Glue workflows, as you would need to write code to implement your business logic, handle errors and retries, and monitor the invocation and execution of your Lambda functions. Moreover, AWS Lambda functions have limitations on the execution time, memory, and concurrency, which may affect the performance and scalability of your ETL workflows.

D. Amazon Managed Workflows for Apache Airflow (Amazon MWAA) workflows. Amazon MWAA is a managed service that makes it easy to run open source Apache Airflow on AWS. Apache Airflow is a popular tool for creating and managing complex ETL pipelines using directed acyclic graphs (DAGs). You can use Amazon MWAA workflows to orchestrate AWS Glue and Amazon EMR jobs as part of your ETL workflows, and use the Airflow web interface to visualize and monitor your workflows. However, this option would have more operational overhead than AWS Glue workflows, as you would need to set up and configure your Amazon MWAA environment, write Python code to define your DAGs, and manage the dependencies and versions of your Airflow plugins and operators.

1: AWS Glue Workflows

2: AWS Glue and Amazon EMR

3: AWS Step Functions

AWS Lambda

Amazon Managed Workflows for Apache Airflow

Problem Analysis:

The company uses Kinesis Data Streams for both inventory management and reordering.

The Kinesis Producer Library (KPL) publishes data, and the Kinesis Client Library (KCL) consumes data.

Duplicate records were observed in the inventory reordering system.

Key Considerations:

Kinesis streams are designed for durability but may produce duplicates under certain conditions.

Factors such as network timeouts, shard splits, or changes in record processors can cause duplication.

Solution Analysis:

Option A: Network-Related Timeouts

If the producer (KPL) experiences network timeouts, it retries data submission, potentially causing duplicates.

Option B: High IteratorAgeMilliseconds

High iterator age suggests delays in processing but does not directly cause duplication.

Option C: Changes in Shards or Processors

Changes in the number of shards or record processors can lead to re-processing of records, causing duplication.

Option D: AggregationEnabled Set to True

AggregationEnabled controls the aggregation of multiple records into one, but it does not cause duplication.

Option E: High max_records Value

A high max_records value increases batch size but does not lead to duplication.

Final Recommendation:

Network-related timeouts and changes in shards or processors are the most likely causes of duplicate data in this scenario.

Amazon Kinesis Data Streams Best Practices

Kinesis Producer Library (KPL) Overview

Kinesis Client Library (KCL) Overview