DEA-C01 Practice Test 25 — 15 Questions

Question 1

A data engineer needs to ingest JSON data from an on-premises relational database into Amazon S3 every hour. Which AWS service should be used to set up a scheduled, incremental data transfer?

Accepted Answer

AWS Database Migration Service (DMS) with S3 as target.. AWS DMS is purpose-built for migrating databases to AWS targets, including Amazon S3. It supports ongoing replication (change data capture) and scheduled full-load tasks, making it ideal for hourly incremental transfers from an on-premises relational database to S3 without custom scripting.

Answer

Amazon S3 Transfer Acceleration with a cron job.

Answer

AWS Glue with a JDBC connection and a scheduled crawler.

Answer

Amazon Kinesis Data Firehose with a database source.

Question 2

A data engineer is troubleshooting a failed AWS Glue job that writes results to Amazon S3. The error log shows 'AccessDenied' when trying to list the bucket. Which IAM policy statement should the engineer add to the Glue job's role?

Accepted Answer

s3:ListBucket. Listing a bucket requires the s3:ListBucket permission. Option B is wrong because s3:PutObject is for writing, not listing. Option C is wrong because s3:DeleteObject is not needed. Option D is wrong because s3:GetObject is for reading objects, not listing.

Answer

s3:PutObject

Answer

s3:DeleteObject

Answer

s3:GetObject

Question 3

A data engineering team is using AWS Glue to catalog data in an S3 data lake. They have a Glue crawler that runs daily to update the Data Catalog. Recently, they noticed that the crawler is taking longer to run and sometimes fails because of a timeout. The team suspects the issue is due to the large number of small files in the S3 bucket. They need to improve crawler performance and reliability. Which solution should they implement?

Accepted Answer

Use AWS Glue ETL to consolidate small files into larger ones before crawling.. Consolidating small files into larger ones (e.g., using AWS Glue ETL with a groupFiles or groupSize option, or a separate compaction job) reduces the number of objects the crawler must list and sample. This directly addresses the root cause: a high volume of small files increases metadata operations and can cause crawler timeouts. By reducing file count, the crawler can complete within the default 24-hour timeout and avoid failures.

Answer

Configure the crawler to use a different classifier.

Answer

Increase the crawler timeout to 24 hours.

Answer

Schedule the crawler to run more frequently to avoid large data accumulation.

Question 4

A company uses AWS Glue to catalog data in Amazon S3. The data arrives in Parquet format, but the crawler fails to update the schema when new columns are added. What is the most likely cause?

Accepted Answer

The crawler configuration has 'Update the table definition' set to 'Ignore the change'.. AWS Glue crawlers have a table-update behavior controlled by the 'Update the table definition in the Data Catalog' setting (SchemaChangePolicy.UpdateBehavior). If it is set to 'Ignore the change' (LOG), the crawler detects new columns but does not modify the table definition, so the schema appears stale. Setting it to 'Update the table definition' (UPDATE_IN_DATABASE) allows the crawler to add new columns to the catalog table.

Answer

The Glue Data Catalog is not configured to accept schema changes.

Answer

Parquet files do not support schema evolution.

Answer

The S3 bucket has versioning disabled.

Question 5

A company uses Amazon Redshift for analytics. The data engineer notices that queries are slow and the system is experiencing high disk usage. The engineer suspects that the distribution style is suboptimal. Which action should the engineer take to improve query performance?

Accepted Answer

Use the DISTSTYLE AUTO setting and analyze query patterns to let Redshift choose.. DISTSTYLE AUTO allows Amazon Redshift to automatically assign distribution styles (KEY, EVEN, or ALL) based on query patterns and table size, optimizing data distribution for improved query performance. This is particularly effective when the engineer suspects suboptimal distribution but lacks detailed knowledge of the ideal key, as Redshift analyzes workload patterns to reduce data movement and disk usage.

Answer

Convert all tables to use SORTKEY on the most frequently filtered column.

Answer

Increase the number of nodes in the cluster to distribute data across more slices.

Answer

Set all tables to DISTSTYLE EVEN to distribute data evenly.

Question 6

A data engineer is designing a multi-Region disaster recovery solution for an Amazon DynamoDB table. The table must be available in a secondary Region with minimal data loss and automatic failover. Which feature should be used?

Accepted Answer

DynamoDB global tables. DynamoDB global tables provide a fully managed, multi-Region, multi-active database solution that replicates data automatically across selected AWS Regions. This ensures automatic failover with eventual consistency and minimal data loss, meeting the disaster recovery requirements for high availability and automatic failover without manual intervention.

Answer

DynamoDB on-demand backup and restore in the secondary Region

Answer

DynamoDB point-in-time recovery (PITR)

Answer

DynamoDB cross-Region snapshot export to S3

Question 7

A data engineer needs to ingest streaming data from an IoT fleet into Amazon S3 for near-real-time analytics. The data volume is approximately 5 GB per hour, and each event is less than 1 KB. Which AWS service should be used as the ingestion endpoint?

Accepted Answer

AWS IoT Core. AWS IoT Core is purpose-built for ingesting data from IoT devices, supporting MQTT, HTTP, and WebSocket protocols. It can handle millions of devices and high-throughput, small-message payloads (each event <1 KB) and integrates directly with Amazon S3 via IoT Core rules, making it the ideal ingestion endpoint for near-real-time analytics on streaming IoT data.

Answer

AWS DataSync

Answer

Amazon AppFlow

Answer

Amazon Kinesis Data Streams

Question 8

A company uses AWS Glue to process data from Amazon RDS MySQL into Amazon S3. The Glue job uses a JDBC connection and runs on a schedule. Recently, the job has been failing with a 'Communications link failure' error. The RDS instance is in a private subnet. Which troubleshooting step should the data engineer take FIRST?

Accepted Answer

Verify that the Glue job's VPC subnet and security group allow outbound traffic to RDS.. The 'Communications link failure' error typically indicates a network connectivity issue between the Glue job and the RDS instance. Since the RDS instance is in a private subnet, the Glue job must be configured with a VPC subnet and security group that allows outbound traffic to the RDS instance's security group on port 3306 (MySQL). Without this network path, the JDBC connection cannot be established, making verifying the VPC and security group configuration the first logical troubleshooting step.

Answer

Check the Glue job's DPU allocation; increase if too low.

Answer

Review the Glue job script for data type mismatches.

Answer

Increase the RDS instance's max_connections parameter.

Question 9

A company wants to migrate on-premises data to Amazon S3 using AWS DataSync. The data is stored on an NFS file server and the total volume is 50 TB. The network bandwidth between the on-premises data center and AWS is 1 Gbps (gigabit per second). What is the primary factor that will determine the total time required for the initial data transfer?

Accepted Answer

The available network bandwidth between on-premises and AWS. AWS DataSync transfers data over the network, so the primary constraint is the available bandwidth between the on-premises NFS server and AWS. With 50 TB of data and a 1 Gbps link, the theoretical minimum transfer time is approximately 50 TB * 8 / 1 Gbps = 400,000 seconds (~111 hours), but real-world throughput is lower due to protocol overhead, latency, and competing traffic. The network bandwidth directly dictates the maximum data transfer rate, making it the dominant factor for the initial transfer duration.

Answer

The number of S3 buckets used as the destination

Answer

The average file size in the dataset

Answer

The IOPS (I/O operations per second) of the on-premises NFS server

Question 10

A data engineer needs to migrate an on-premises Apache Hadoop cluster to AWS. The cluster stores data in HDFS and runs MapReduce jobs. The company wants to minimize operational overhead and leverage serverless technologies where possible. Which AWS service should the data engineer use to replace HDFS storage?

Accepted Answer

Amazon S3. Amazon S3 is the correct replacement for HDFS because it provides highly durable, scalable, and serverless object storage that can be used as the primary storage layer for Amazon EMR. Unlike HDFS, S3 decouples storage from compute, eliminating the need to manage cluster storage and allowing jobs to run on ephemeral clusters, which minimizes operational overhead. S3 integrates with EMR via the EMR File System (EMRFS), enabling MapReduce jobs to read/write data directly from S3 as if it were HDFS.

Answer

Amazon EBS

Answer

Amazon EMR

Answer

Amazon Redshift

Question 11

Order the steps to troubleshoot a failed AWS Glue job that reads from JDBC and writes to S3.

Accepted Answer

Check AWS Glue job logs, then verify network connectivity, then verify IAM permissions, then test JDBC connection, then review the Glue script.. Start with logs to identify errors, then check connectivity, IAM permissions, test connection, and review script.

Answer

Verify IAM permissions, then check AWS Glue job logs, then verify network connectivity, then test JDBC connection, then review the Glue script.

Answer

Test JDBC connection, then check AWS Glue job logs, then verify network connectivity, then verify IAM permissions, then review the Glue script.

Answer

Review the Glue script, then check AWS Glue job logs, then verify network connectivity, then verify IAM permissions, then test JDBC connection.

Question 12

Which TWO actions are recommended for securing data at rest in Amazon S3? (Choose two.)

Accepted Answer

Enable default encryption on the S3 bucket using SSE-S3 or SSE-KMS.. Option A is correct because enabling default bucket encryption with SSE-S3 or SSE-KMS ensures that every object written to the bucket is automatically encrypted at rest, satisfying the core requirement for data-at-rest protection in Amazon S3. Option D is correct because a bucket policy that denies PutObject requests lacking the x-amz-server-side-encryption header enforces encryption on upload, preventing unencrypted objects from being stored even if default encryption is bypassed or misconfigured. Option B is not a security control; S3 Bucket Key reduces AWS KMS request costs and CloudTrail event volume but does not itself secure data at rest. Option C addresses availability and data durability against accidental deletion through versioning, not encryption at rest. Option E provides geographic redundancy and disaster recovery via cross-region replication, but replication does not encrypt data at rest by itself.

Answer

Use S3 Bucket Key to reduce KMS request costs.

Answer

Enable S3 Versioning to protect against accidental deletions.

Answer

Configure cross-region replication to replicate data to another bucket.

Question 13

A company runs an Amazon Redshift cluster with 10 RA3 nodes. The data warehouse stores 50 TB of data. The company notices that queries are slow and the cluster's storage utilization is high. The data engineer needs to improve query performance and reduce storage costs without changing the cluster's node count. Which action should the engineer take?

Accepted Answer

Use Redshift Spectrum to offload historical data to Amazon S3 and query it in place.. Redshift Spectrum allows you to query data directly from Amazon S3 without loading it into the cluster. By offloading historical or less-frequently accessed data to S3, you reduce the storage utilization on the RA3 nodes, which frees up managed storage and can improve query performance. This approach also lowers storage costs because S3 is cheaper than Redshift managed storage, and it does not change the node count.

Answer

Change the distribution style of large tables to DISTSTYLE ALL.

Answer

Migrate the cluster to Dense Compute node types.

Answer

Enable concurrency scaling to handle more concurrent queries.

Question 14

A data engineer needs to set up a data catalog for a new data lake in AWS Glue. The data resides in S3 in Parquet format. The engineer wants to ensure that the schema is automatically detected and updated when new columns are added to the data. Which configuration should the engineer use?

Accepted Answer

Configure the crawler's 'Schema updates' option to 'Update the table schema'.. The Glue crawler's 'Schema updates' option controls what happens when the crawler detects schema changes in the data. Setting it to 'Update the table schema' allows the crawler to add new columns and modify the existing table definition in the Data Catalog when new columns appear in the Parquet files. This is the correct configuration for automatic schema evolution.

Answer

Add a partition index to the Glue Data Catalog table.

Answer

Set the crawler's 'Database' output to a new database.

Answer

Enable partition indexing on the table.

Question 15

Refer to the exhibit. A data engineer is configuring an AWS Lambda function to process records from a Kinesis stream. The function is set up with an event source mapping, but no records are being processed. The Lambda function's IAM role has the policy shown. What is the most likely reason for the issue?

Accepted Answer

The IAM policy does not include all the necessary Kinesis actions for the event source mapping to work.. The most likely reason is that the IAM policy does not include all necessary Kinesis actions for the event source mapping to work. Lambda's event source mapping requires permissions to perform actions like `kinesis:GetRecords`, `kinesis:GetShardIterator`, `kinesis:DescribeStream`, and `kinesis:ListStreams`. If any of these are missing, the mapping cannot poll the stream, resulting in no records processed.

Answer

The policy does not grant permission to describe the Kinesis stream.

Answer

The policy includes too many actions, which causes a conflict.

Answer

The resource ARN for the Lambda function in the policy is incorrect.