DEA-C01 Data Operations and Support Practice Test 8 — 15 Questions

Question 1

A data engineer needs to troubleshoot a failed AWS Glue job that reads from an Amazon RDS for MySQL database. The error log shows 'Communications link failure'. Which step should the engineer take FIRST?

Accepted Answer

Check that the security group associated with the Glue job allows outbound traffic to the RDS database.. Option B is correct because a 'Communications link failure' often indicates network connectivity issues; verifying that the Glue job's security group allows outbound traffic to the RDS database is the first troubleshooting step. Option A is wrong because the error is not about authentication. Option C is wrong because the issue is not about table structure. Option D is wrong because the error is not about permissions.

Answer

Increase the job timeout and retry count.

Answer

Verify that the database username and password are correct in the Glue connection.

Answer

Confirm that the table schema in MySQL matches the Glue Data Catalog.

Question 2

A company uses AWS DMS to migrate a 2 TB Oracle database to Amazon RDS for PostgreSQL. The migration completes successfully, but data validation shows some tables have missing rows. The task is configured for ongoing replication using change data capture (CDC). What is the MOST likely cause of the missing rows?

Accepted Answer

Source tables missing primary keys. Option C is correct because if a table lacks a primary key, DMS cannot uniquely identify rows for CDC, leading to missed changes. Option A is wrong because the endpoint connection is valid (migration completed). Option B is wrong because CDC captures changes from redo logs, not the source database directly. Option D is wrong because DMS supports large objects with proper configuration.

Answer

Source database archive log retention period too short

Answer

Large objects (LOBs) not supported by the target

Answer

Insufficient storage on the DMS replication instance

Question 3

A company uses Amazon EMR to process large datasets stored in Amazon S3. The data engineer notices that EMR tasks are failing with 'DiskOutOfSpace' errors. The cluster uses m5.xlarge instances with 1 EBS volume of 64 GB. What is the MOST cost-effective solution to resolve this issue?

Accepted Answer

Increase the EBS storage volume size for each instance and use spot instances for task nodes.. Option D is correct because increasing EBS storage per instance provides more disk space, and using spot instances reduces cost. Option A is wrong because adding more instances may not address the per-instance disk space issue and increases cost. Option B is wrong because increasing core nodes only helps if the shuffle data is distributed; spot instances reduce cost but may cause interruptions. Option C is wrong because switching to D2 instances is more expensive and may not be needed.

Answer

Use a mix of on-demand and spot instances for core nodes.

Answer

Switch to D2 instances which have more instance store volume.

Answer

Increase the number of task instances to distribute the workload.

Question 4

A data engineer is optimizing an Amazon Redshift cluster that runs a nightly ETL workload. The engineer notices that the query performance degrades over the week and improves after a VACUUM operation. Which action should the engineer take to automate this maintenance and minimize impact on performance?

Accepted Answer

Schedule a VACUUM command using a query scheduler like Amazon EventBridge.. Option B is correct because automating VACUUM using a scheduled query (e.g., via Amazon EventBridge or Redshift's built-in scheduler) ensures regular maintenance without manual intervention. Option A is wrong because disabling auto vacuum does not automate it. Option C is wrong because dropping and recreating tables is disruptive. Option D is wrong because manual VACUUM is not automated.

Answer

Run VACUUM manually only when performance degrades significantly.

Answer

Disable auto vacuum and run a manual VACUUM every night after the ETL.

Answer

Drop and recreate the tables weekly to avoid unsorted data.

Question 5

A team uses Amazon Kinesis Data Analytics to process streaming data. They notice that the application's output is delayed. Which AWS service can be used to monitor the application's performance and identify bottlenecks?

Accepted Answer

Amazon CloudWatch. Option A is correct because CloudWatch provides metrics and logs for Kinesis Data Analytics applications. Option B is wrong because CloudTrail records API calls, not performance metrics. Option C is wrong because Athena is an interactive query service. Option D is wrong because X-Ray traces requests but is not the primary service for monitoring Kinesis Data Analytics performance.

Answer

AWS CloudTrail

Answer

Amazon Athena

Answer

AWS X-Ray

Question 6

A data engineer is troubleshooting an AWS Glue job that reads from an Apache Kafka topic using a Glue connector. The job fails with 'TimeoutException'. The Kafka cluster is in a VPC. Which step should the engineer take FIRST?

Accepted Answer

Check the security group and network ACLs associated with the Glue job's VPC.. Option C is correct because timeout errors often indicate network connectivity issues; verifying the security group and route tables for the Glue job's VPC is the first step. Option A is wrong because the error is not about the connector library. Option B is wrong because the job type does not cause timeouts. Option D is wrong because the error is not about record format.

Answer

Increase the Kafka consumer session timeout.

Answer

Update the Glue connector to the latest version.

Answer

Change the Glue job type from Spark to Python Shell.

Question 7

A company runs a daily batch process that reads data from Amazon S3, transforms it with AWS Glue, and loads it into Amazon Redshift. The process takes 6 hours, but the business requires completion within 4 hours. Which design change would MOST reduce runtime?

Accepted Answer

Load data directly from S3 to Redshift using COPY command, then transform in Redshift. Option D is correct because using Redshift's COPY command with S3 is optimized for bulk loads and avoids transformation delays. Option A is wrong because increasing Glue workers may help but doesn't address Redshift load speed. Option B is wrong because columnar storage is already used. Option C is wrong because S3 Select reduces data scanned but does not accelerate the Glue job.

Answer

Increase the number of Glue workers

Answer

Use S3 Select to filter data before Glue

Answer

Switch to columnar storage in Redshift

Question 8

A company uses Amazon S3 to store raw data files. An AWS Glue crawler creates metadata in the Data Catalog. The data engineer discovers that the crawler is not detecting new partitions after new data is added to the S3 bucket. What is the MOST likely cause?

Accepted Answer

The IAM role used by the crawler does not have kms:Decrypt permission for the KMS key that encrypts the new partitions.. Option B is correct because if the S3 bucket uses an SSE-KMS encrypted prefix, the crawler may not have permission to decrypt; the KMS key policy or IAM role must allow kms:Decrypt. Option A is wrong because S3 events are not required for crawling. Option C is wrong because the crawler can handle many objects. Option D is wrong because the crawler configuration may need to be set to detect partitions, but the most likely cause given encryption is permission.

Answer

The crawler configuration has 'Crawl all folders' disabled.

Answer

The S3 bucket has too many objects, exceeding the crawler's limit.

Answer

The crawler does not have S3 event notifications enabled.

Question 9

A data engineer is troubleshooting an AWS Step Functions workflow that calls a Lambda function to process data. The workflow sometimes fails with a 'StateMachineExecutionLimitExceeded' error. What is the MOST likely cause?

Accepted Answer

Number of concurrent executions exceeds the account limit. Option C is correct because Step Functions has a default execution limit per account; hitting it causes this error. Option A is wrong because Lambda concurrency limits cause throttling errors, not state machine execution limits. Option B is wrong because execution time limits cause 'ExecutionTimedOut' errors. Option D is wrong because the error is specific to state machine executions, not Lambda.

Answer

Execution time exceeds the maximum allowed duration

Answer

Lambda function memory limit exceeded

Answer

Lambda function concurrency limit reached

Question 10

A data engineer is monitoring an Amazon Redshift cluster using Amazon CloudWatch. The engineer notices that the 'WriteThroughput' metric is consistently below the provisioned IOPS for the cluster's EBS volumes. The query performance is slower than expected. Which action is MOST likely to improve write performance?

Accepted Answer

Upgrade to a larger node type with more CPU and memory.. Option D is correct because if write throughput is low but IOPS are not saturated, the bottleneck may be CPU or memory; increasing the node size (DC2 or RA3) provides more CPU and memory. Option A is wrong because increasing IOPS when not saturated won't help. Option B is wrong because concurrency may cause blocking but not necessarily low throughput. Option C is wrong because sort keys improve read performance, not write.

Answer

Reduce the number of concurrent queries to the database.

Answer

Add sort keys to the tables to improve data distribution.

Answer

Increase the provisioned IOPS on the EBS volumes.

Question 11

A company stores sensitive data in Amazon S3. To meet compliance requirements, they need to ensure that any data older than 1 year is automatically moved to a lower-cost storage class. Which S3 feature should they use?

Accepted Answer

S3 Lifecycle policies. Option B is correct because S3 Lifecycle policies automate transitioning objects between storage classes. Option A is wrong because S3 Glacier is a storage class, not a feature to automate transitions. Option C is wrong because S3 Intelligent-Tiering automatically optimizes costs but does not enforce a specific age-based transition. Option D is wrong because S3 Replication is for copying objects across buckets.

Answer

S3 Replication

Answer

S3 Glacier

Answer

S3 Intelligent-Tiering

Question 12

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. Option A is correct because 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:GetObject is for reading objects. Option D is wrong because s3:DeleteObject is not needed.

Answer

s3:PutObject

Answer

s3:DeleteObject

Answer

s3:GetObject

Question 13

A data engineer uses Amazon EMR to run a Spark job that reads from S3 and writes to HDFS on the cluster. The job fails with an 'OutOfMemoryError: Java heap space' error in the executors. Which parameter adjustment should be made to resolve this?

Accepted Answer

Increase spark.executor.memory. Option A is correct because increasing spark.executor.memory allocates more heap space to executors. Option B is wrong because spark.driver.memory affects the driver, not executors. Option C is wrong because spark.sql.shuffle.partitions affects shuffle behavior, not memory. Option D is wrong because spark.default.parallelism controls task parallelism, not memory.

Answer

Increase spark.default.parallelism

Answer

Increase spark.sql.shuffle.partitions

Answer

Increase spark.driver.memory

Question 14

A data engineer is designing a disaster recovery strategy for an Amazon RDS for PostgreSQL database that is used in a data pipeline. The database must have a Recovery Point Objective (RPO) of less than 1 minute and a Recovery Time Objective (RTO) of less than 5 minutes. Which TWO actions should the engineer take?

Accepted Answer

Enable automated backups with point-in-time recovery.. Options B and D are correct. Multi-AZ with standby provides automatic failover with RTO typically under 1-2 minutes, and automated backups with point-in-time recovery enable RPO of seconds. Option A is wrong because read replicas are not for automatic failover. Option C is wrong because snapshots are manual and have higher RPO/RTO. Option E is wrong because cross-Region replication adds latency and may not meet RPO.

Answer

Take frequent manual snapshots and copy them to another Region.

Answer

Create a read replica in a different Availability Zone.

Answer

Use cross-Region replication with Amazon Aurora Global Database.

Question 15

A company runs a data lake on Amazon S3 with AWS Glue and Amazon Athena. The data engineer notices that queries are slow and scanning large amounts of data. Which THREE actions should the engineer take to optimize query performance and reduce costs?

Accepted Answer

Compress data files using gzip or snappy.. Options A, B, and D are correct. Partitioning reduces data scanned, compressing files reduces scan size, and converting to columnar formats (Parquet) improves performance and reduces cost. Option C is wrong because more workers would increase cost. Option E is wrong because increasing timeout does not improve performance or reduce cost.

Answer

Increase the query timeout in Athena.

Answer

Increase the number of DPUs in the Glue job.