DEA-C01 Mock Exam 94 — 25 Questions

Question 1

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The primary instance fails, and automatic failover occurs. After failover, the application experiences higher latency. What is the most likely cause?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The new primary instance is in a different Availability Zone, increasing network latency.. After a Multi-AZ failover in Amazon RDS for MySQL, the new primary instance is launched in a different Availability Zone (AZ) than the original primary. If the application's compute resources (e.g., EC2 instances) remain in the original AZ, cross-AZ network traffic incurs additional latency due to the physical distance and the need to traverse the AZ boundary, which typically adds 1–2 ms of round-trip time. This increased network latency directly impacts application performance, especially for latency-sensitive queries.

Answer

The read replica is now the primary and cannot handle write traffic.

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The failover process disabled automatic backups.

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The DNS endpoint did not update to point to the new primary.

Question 2

A company is designing a data lake on Amazon S3. The data includes CSV files, Parquet files, and images. The data engineering team needs to catalog the metadata and enable SQL queries. Which TWO AWS services should be used together?

Accepted Answer

Amazon Athena. Amazon Athena is correct because it is a serverless interactive query service that can directly query data stored in Amazon S3 using standard SQL, without needing to load or transform data. AWS Glue is correct because it provides a fully managed data catalog (AWS Glue Data Catalog) that stores metadata about the data lake's schema, partitions, and locations, which Athena can use to discover and query the data efficiently.

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Amazon EMR

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Amazon Redshift Spectrum

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Amazon QuickSight

Question 3

A data engineer receives an alert that a Kinesis Data Stream has a 'WriteProvisionedThroughputExceeded' error. The stream has 5 shards with 1 MB/s write capacity per shard. The producer application is sending data at 8 MB/s sustained. What should the engineer do to resolve the issue?

Accepted Answer

Increase the number of shards from 5 to 10.. The 'WriteProvisionedThroughputExceeded' error indicates that the total write throughput to the Kinesis Data Stream exceeds the provisioned capacity. With 5 shards, each offering 1 MB/s write capacity, the total write capacity is 5 MB/s. The producer is sending 8 MB/s, which is above this limit. Increasing the number of shards to 10 raises the total write capacity to 10 MB/s, accommodating the sustained 8 MB/s throughput and resolving the throttling.

Answer

Reduce the record size to below 1 MB per record.

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Enable enhanced fan-out on the stream.

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Use Kinesis Firehose as an intermediary to buffer data.

Question 4

A company is using an RDS for PostgreSQL instance and wants to minimize downtime during a major version upgrade. Which approach should be taken?

Accepted Answer

Create a read replica of the DB instance, upgrade the replica, and then promote it to the primary instance.. Creating a read replica of the RDS for PostgreSQL instance, upgrading the replica to the new major version, and then promoting it to become the primary instance minimizes downtime by allowing the replica to be upgraded while the original primary remains fully operational. The promotion process is fast (typically seconds), and the only downtime is the brief cutover period when applications switch to the promoted replica. This approach leverages RDS's managed replication and avoids the longer downtime associated with direct in-place upgrades.

Answer

Use AWS Database Migration Service (DMS) to migrate data to a new upgraded instance.

Answer

Modify the DB instance and apply the upgrade immediately.

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Take a snapshot of the DB instance and restore it as a new instance with the upgraded version.

Question 5

A data engineer needs to store semi-structured JSON files that are accessed infrequently but must be retrievable within minutes. The data is immutable and must be stored cost-effectively. Which AWS service should the engineer use?

Accepted Answer

Amazon S3 with S3 Standard-IA storage class. Amazon S3 Standard-IA (Infrequent Access) is designed for data that is accessed less frequently but requires rapid retrieval when needed, with retrieval times in milliseconds. It offers lower storage costs than S3 Standard while maintaining high durability and availability, making it ideal for storing immutable semi-structured JSON files that must be retrievable within minutes. The service is cost-effective for infrequently accessed data because it charges a retrieval fee per GB, but the storage price is significantly lower than standard tiers.

Answer

Amazon DynamoDB with on-demand capacity

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Amazon EBS with gp3 volume

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Amazon RDS for PostgreSQL with JSONB data type

Question 6

A company uses Amazon S3 to store sensitive data. The security team requires that all data be encrypted at rest using a customer-managed key that is rotated annually. Which encryption option should be used?

Accepted Answer

SSE-KMS (Server-Side Encryption with AWS KMS).. SSE-KMS is the correct choice because it allows you to use a customer-managed key (CMK) in AWS KMS, which you can configure to rotate automatically on an annual schedule. This satisfies the security team's requirement for encryption at rest with a key you control and rotate yearly, while still leveraging server-side encryption that integrates with S3's existing infrastructure.

Answer

SSE-S3 (Server-Side Encryption with S3-managed keys).

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Client-side encryption.

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SSE-C (Server-Side Encryption with Customer-Provided keys).

Question 7

A company is using Amazon DynamoDB for a gaming application. They want to store player session data that expires after 24 hours. Which DynamoDB feature should be used?

Accepted Answer

Time to Live (TTL). Amazon DynamoDB Time to Live (TTL) allows you to define a per-item timestamp attribute that automatically deletes items after a specified duration. For the gaming session data that must expire after 24 hours, you can set the TTL attribute to the current time plus 24 hours, and DynamoDB will asynchronously delete expired items without any additional cost or write operations.

Answer

DynamoDB Streams

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Global Tables

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Point-in-Time Recovery

Question 8

A company is using Amazon Redshift for data warehousing. The data engineer notices that the STL_ALERT_EVENT_LOG table shows many 'missing statistics' alerts. What is the best course of action to address this issue?

Accepted Answer

Run ANALYZE on the tables.. The STL_ALERT_EVENT_LOG table records alerts about query performance issues, including 'missing statistics' alerts. This indicates that the query optimizer lacks up-to-date table statistics, leading to suboptimal query plans. Running the ANALYZE command updates table statistics, enabling the optimizer to generate efficient execution plans. Therefore, option D is the correct course of action.

Answer

Increase the WLM concurrency slots.

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Run VACUUM on the tables.

Answer

Enable compression on the tables.

Question 9

A company is migrating an on-premises MongoDB database to Amazon DocumentDB. The data engineer needs to ensure minimal downtime during migration. Which AWS service should be used to facilitate the migration?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) supports continuous replication from MongoDB to Amazon DocumentDB using change data capture (CDC), enabling near-zero downtime migration. DMS can perform a full load followed by ongoing replication to keep the target synchronized until cutover.

Answer

AWS Glue

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AWS Snowball

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Amazon S3 Transfer Acceleration

Question 10

A company is using Amazon S3 for data lake storage. They need to query the data directly using SQL without loading it into a database. Which AWS service should be used?

Accepted Answer

Amazon Athena. Amazon Athena is the correct choice because it is a serverless, interactive query service that allows you to analyze data directly in Amazon S3 using standard SQL, without needing to load or transform the data into a database. Athena uses Presto under the hood and supports querying structured, semi-structured, and unstructured data formats (e.g., CSV, JSON, Parquet, ORC) stored in S3, making it ideal for ad-hoc SQL queries on a data lake.

Answer

Amazon Redshift Spectrum

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Amazon EMR

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AWS Glue

Question 11

A data engineer is configuring an Amazon S3 lifecycle policy to transition objects to S3 Glacier Deep Archive after 90 days. The bucket receives new objects daily. The engineer wants to ensure that objects are not deleted before 90 days. Which lifecycle action should be used?

Accepted Answer

Transition. (Transition) is correct because the S3 Lifecycle Transition action moves objects between storage classes over time. To ensure objects are moved to S3 Glacier Deep Archive after 90 days without deletion, a Transition rule is configured to specify the target storage class and the number of days from object creation.

Answer

Expiration

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NoncurrentVersionTransition

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AbortIncompleteMultipartUpload

Question 12

A company wants to ingest streaming data from thousands of IoT devices into AWS for real-time analytics. Which AWS service is best suited for this purpose?

Accepted Answer

Amazon Kinesis Data Streams. Amazon Kinesis Data Streams is purpose-built for ingesting and processing streaming data at scale from thousands of sources. It can capture and store terabytes of data per hour from IoT devices, enabling real-time analytics with millisecond latencies. The service provides durable, ordered data streams that can be consumed by multiple applications simultaneously.

Answer

Amazon S3

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AWS Lambda

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Amazon RDS

Question 13

A company is using Amazon RDS for MySQL and needs to automate backups with a retention period of 35 days. They also want to be able to restore to any point within the retention period. Which configuration should be used?

Accepted Answer

Set the backup retention period to 35 days and enable automatic backups.. Amazon RDS for MySQL supports automated backups with a configurable retention period of up to 35 days. By setting the backup retention period to 35 days and enabling automatic backups, RDS automatically performs daily snapshots and transaction log backups, enabling point-in-time recovery (PITR) to any second within the retention window. This meets the requirement for both a 35-day retention and full PITR capability without manual intervention.

Answer

Enable manual snapshots daily and retain for 35 days.

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Set the backup retention period to 7 days and create daily manual snapshots.

Answer

Disable automated backups and rely on Multi-AZ for recovery.

Question 14

A data engineer is troubleshooting an AWS Glue job that reads from an Amazon RDS for PostgreSQL database using a JDBC connection. The job fails with the error 'java.sql.SQLException: No suitable driver'. Which TWO actions should the engineer take to resolve this issue? (Select TWO.)

Accepted Answer

Verify that the connection string in the job's JDBC URL uses the correct format and includes the driver class. The 'No suitable driver' error in JDBC indicates that the driver class specified in the JDBC URL is either missing or incorrect. For PostgreSQL, the JDBC URL must follow the format 'jdbc:postgresql://host:port/database' and the driver class must be 'org.postgresql.Driver'. If the URL is malformed or the driver class is not properly referenced, the Glue job cannot load the driver, leading to this specific SQLException.

Answer

Check that the Glue job's VPC and security groups allow outbound traffic to the RDS instance

Answer

Restart the Glue job with a higher timeout value

Answer

Update the IAM role associated with the Glue job to allow 'rds:*' permissions

Question 15

A data engineer is troubleshooting an access denied error when an AWS Lambda function tries to decrypt an object encrypted with the KMS key 'abc123'. The Lambda function's execution role has the above policy attached. What is the likely cause of the error?

Accepted Answer

The KMS key policy does not grant the Lambda role decrypt permission. The error occurs because KMS requires both the IAM policy and the key policy to grant the necessary permissions. While the IAM policy attached to the Lambda execution role includes kms:Decrypt, the KMS key policy for 'abc123' does not explicitly grant the Lambda role permission to call kms:Decrypt. Since KMS key policies act as a resource-based policy, they must allow the principal (the Lambda role) to perform the action; otherwise, the request is denied even if the IAM policy allows it.

Answer

The Deny statement blocks all decrypt requests

Answer

The Lambda function does not have permission to call kms:GenerateDataKey

Answer

The IAM policy does not include kms:Decrypt permission

Question 16

A company uses Amazon DynamoDB as the primary data store for a gaming application. The application stores user profiles and game state. During peak hours, the application experiences throttling on writes to the UserProfiles table. The table's read capacity is underutilized. Which solution should resolve the write throttling?

Accepted Answer

Increase the provisioned write capacity units for the table.. Write throttling occurs when the number of write requests exceeds the provisioned write capacity units (WCUs) for the DynamoDB table. Since the read capacity is underutilized, the correct solution is to increase the provisioned WCUs to accommodate the peak write traffic. This directly addresses the capacity deficit without affecting read operations.

Answer

Enable DynamoDB Accelerator (DAX) on the table.

Answer

Add a global secondary index (GSI) to the table.

Answer

Configure auto scaling for read capacity units.

Question 17

A company runs an Amazon RDS for PostgreSQL instance that stores financial data. The company requires point-in-time recovery (PITR) with a retention period of 35 days. Additionally, the company needs to create a new database from a specific snapshot every night for testing. Which combination of actions should the data engineer take to meet these requirements?

Accepted Answer

Enable automated backups with a 35-day retention period and create a manual snapshot each night for testing.. Automated backups in Amazon RDS for PostgreSQL support a maximum retention period of 35 days, which satisfies the PITR requirement. Additionally, creating a manual snapshot each night provides a stable, independent copy for testing without interfering with the automated backup schedule or the source database's performance.

Answer

Create a read replica and promote it to a new instance for testing each night.

Answer

Enable Multi-AZ and use the standby instance for testing.

Answer

Disable automated backups to reduce storage costs and take manual snapshots with 35-day retention.

Question 18

A data engineer needs to store log files from multiple applications in a centralized location. The logs are generated in JSON format and each log entry is about 1 KB. The engineer needs to query the logs occasionally using SQL-like queries. Which AWS service is most appropriate?

Accepted Answer

Amazon Athena with data stored in S3. Amazon Athena is the most appropriate service because it allows you to query log files stored in S3 directly using standard SQL, without needing to load or transform the data. Since the logs are in JSON format and each entry is about 1 KB, Athena's schema-on-read approach works perfectly for occasional SQL-like queries, and you only pay for the data scanned per query, making it cost-effective for infrequent access.

Answer

Amazon DynamoDB

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL

Question 19

A data engineer is troubleshooting a slow Amazon Redshift query that joins a large fact table with several dimension tables. The EXPLAIN plan shows a hash join on the distribution key, but the query still runs slowly. The fact table is distributed by KEY(column_x) and the dimension tables are distributed ALL. The engineer notices that the fact table has a high number of rows with the same value in column_x. What is the most likely cause of the slow performance?

Accepted Answer

The fact table's distribution key column has data skew, causing uneven data distribution across nodes.. Data skew in the distribution key column_x causes some slices to hold a disproportionate number of rows, leading to uneven workload distribution during the hash join. The EXPLAIN plan shows a hash join on the distribution key, which should be efficient if data is evenly distributed, but skew forces the node with the most rows to become a bottleneck, slowing the entire query.

Answer

The dimension tables should be distributed by KEY instead of ALL.

Answer

The Redshift cluster does not have enough disk space.

Answer

The fact table does not have a sort key.

Question 20

Refer to the exhibit. A data engineer runs the above command and sees that the DataLakeAdmin role has the AmazonS3FullAccess and AWSLakeFormationDataAdmin policies attached. The engineer wants to ensure that the role can only access S3 data through Lake Formation. What should the engineer do?

Accepted Answer

Detach the AmazonS3FullAccess policy from the role. To enforce that access is only through Lake Formation, the engineer should detach the AmazonS3FullAccess policy because it allows direct S3 access, bypassing Lake Formation. The LakeFormationAdmin policy is needed for Lake Formation administration. Changing the S3 bucket policy to deny all access except from Lake Formation is not straightforward because Lake Formation uses the principal's IAM role. Creating a new policy that denies S3 access would be redundant if the full access policy is removed.

Answer

Create a new IAM policy that explicitly denies s3:GetObject and attach it to the role

Answer

Detach the AWSLakeFormationDataAdmin policy from the role

Answer

Modify the S3 bucket policy to deny all access except from Lake Formation