DEA-C01 Data Store Management Practice Test 5 — 15 Questions

Question 1

A media company stores large video files in Amazon S3 and uses Amazon CloudFront for content delivery. Users in different regions report slow download speeds for popular content. The data engineer needs to improve performance while minimizing cost. Which solution should the engineer implement?

Accepted Answer

Enable CloudFront Origin Shield. CloudFront Origin Shield acts as a centralized caching layer in front of the S3 origin, reducing the number of requests that reach the origin and improving cache hit ratios. This minimizes latency for users in different regions by serving popular content from the edge or shield cache, while also reducing origin load and data transfer costs.

Answer

Change the S3 storage class to S3 Standard-IA

Answer

Enable S3 Transfer Acceleration on the bucket

Answer

Create multiple S3 buckets in different regions and configure CloudFront with multiple origins

Question 2

A data engineer is designing a data lake on Amazon S3. The data includes customer PII that must be encrypted at rest. The company also requires that the encryption keys be rotated automatically every year. Which encryption solution should the engineer use?

Accepted Answer

SSE-KMS with automatic key rotation enabled. SSE-KMS with automatic key rotation enabled meets both requirements: it encrypts data at rest in S3 and allows the company to automatically rotate the customer master key (CMK) every year. AWS KMS supports automatic annual rotation for symmetric CMKs, which satisfies the compliance need without manual intervention.

Answer

SSE-S3

Answer

SSE-C

Answer

Client-side encryption with AWS KMS

Question 3

A company is running a production Amazon Aurora PostgreSQL database. The database experiences high write latency during peak hours. The data engineer suspects that the issue is due to a large number of small transactions. Which action would MOST effectively reduce write latency?

Accepted Answer

Increase the instance size and use Provisioned IOPS storage. Increasing the instance size and using Provisioned IOPS storage directly addresses high write latency by providing more CPU and memory resources to handle transaction processing, while Provisioned IOPS ensures consistent, low-latency I/O for write operations. This is the most effective action because small transactions create high I/O demand, and scaling up the instance with dedicated IOPS reduces contention and write queue depth.

Answer

Enable parallel query for the database

Answer

Enable Aurora Auto Scaling for read replicas

Answer

Enable Performance Insights to identify the bottleneck

Question 4

A data engineer is migrating an on-premises Apache Hive data warehouse to Amazon EMR. The warehouse contains partitioned tables stored in HDFS. The engineer wants to use Amazon S3 as the storage layer for the EMR cluster. What is the MOST important consideration for maintaining query performance on S3?

Accepted Answer

Ensure that the table partitions are organized in a way that minimizes S3 LIST requests. When using Amazon S3 as the storage layer for an EMR cluster, the most critical factor for query performance is minimizing S3 LIST requests. S3 LIST operations are significantly slower and more expensive than GET requests, and Hive/Spark queries on partitioned tables often issue LIST requests to discover partition locations. By organizing partitions with a common prefix (e.g., `year=2023/month=01/day=15/`) and using partition pruning, you reduce the number of LIST calls, directly improving query latency and reducing S3 API costs.

Answer

Configure EMR to use HDFS for storage instead of S3 for better performance

Answer

Use DynamoDB as the Hive metastore to improve metadata access

Answer

Use Amazon Redshift Spectrum to query the data directly from S3

Question 5

A company needs to store application log files for 90 days for compliance. The logs are generated continuously and are rarely accessed after 30 days. The data engineer must minimize storage costs. Which storage solution should the engineer choose?

Accepted Answer

Amazon S3 Standard with a lifecycle policy to transition to S3 Standard-IA after 30 days and expire after 90 days. Amazon S3 Standard with a lifecycle policy to transition to S3 Standard-IA after 30 days and expire after 90 days is correct because it aligns with the access pattern: logs are frequently accessed only in the first 30 days, then rarely accessed for the remaining 60 days. S3 Standard-IA offers lower storage costs for infrequently accessed data while still providing millisecond retrieval, and the lifecycle policy automates the transition and eventual deletion, minimizing costs without sacrificing availability.

Answer

Amazon CloudWatch Logs with a retention policy of 90 days

Answer

Amazon S3 Glacier Deep Archive

Answer

Amazon EBS gp3 volumes attached to an EC2 instance

Question 6

A company is using Amazon DynamoDB with on-demand capacity for a gaming application that experiences unpredictable traffic spikes. The application consistently sees 'ProvisionedThroughputExceededException' errors during spikes. The data engineer needs to resolve this issue without changing the application code. What should the engineer do?

Accepted Answer

Switch the table to on-demand capacity mode. The application is already using on-demand capacity, but the error 'ProvisionedThroughputExceededException' indicates the table is actually in provisioned mode, not on-demand. Switching to on-demand capacity mode eliminates throttling by automatically scaling throughput to match traffic spikes, with no code changes required.

Answer

Enable DynamoDB Accelerator (DAX) to cache read requests

Answer

Increase the read capacity units

Answer

Enable auto scaling for the table with a higher maximum capacity

Question 7

A company is designing a data store for IoT sensor data that is written once and never updated. The data must be stored with high durability and low cost. Which TWO AWS storage services are most suitable? (Choose TWO.)

Accepted Answer

Amazon S3. Amazon S3 is correct because it provides 99.999999999% (11 9's) durability, is designed for write-once-read-many (WORM) workloads, and offers low-cost storage tiers suitable for IoT sensor data that is never updated. S3's object storage model and lifecycle policies allow automatic transition to colder storage, making it ideal for immutable data at scale.

Answer

Amazon ElastiCache

Answer

Amazon EBS

Answer

Amazon DynamoDB

Question 8

A company is using Amazon Redshift for a data warehouse. The data engineer needs to improve query performance for a table that is frequently joined with other tables on a specific column. Which THREE actions would help improve join performance? (Choose THREE.)

Accepted Answer

Set the distribution style to KEY on the join column. Setting the distribution style to KEY on the join column (option A) ensures that rows with the same join key value are co-located on the same compute node. This allows Redshift to perform a collocated join, avoiding the expensive redistribution of data across the network during query execution, which significantly improves join performance.

Answer

Use DISTSTYLE ALL to replicate the table to all nodes

Answer

Change the column data type to a fixed-length CHAR

Question 9

A data engineer is setting up an Amazon RDS for MySQL database. The database must be highly available and automatically failover in case of an AZ outage. Which TWO configurations should the engineer enable? (Choose TWO.)

Accepted Answer

Multi-AZ deployment. Multi-AZ deployment (Option A) automatically provisions and maintains a synchronous standby replica in a different Availability Zone (AZ). In the event of an AZ outage, Amazon RDS automatically fails over to the standby, ensuring high availability with minimal downtime. This is the core mechanism for automatic failover in RDS for MySQL.

Answer

Enhanced Monitoring

Answer

Automated backups with a retention period of 30 days

Answer

Read replicas in a different Region

Question 10

A data engineer applies the bucket policy shown in the exhibit to an S3 bucket. The bucket contains sensitive data that must be encrypted at rest and accessed only over HTTPS. Which of the following statements is true?

Accepted Answer

The policy enforces that all PutObject requests must include the x-amz-server-side-encryption header with value AES256.. Option C is correct because the bucket policy includes a condition that denies PutObject requests unless the `s3:x-amz-server-side-encryption` header is present and set to `AES256`. This enforces server-side encryption with S3-managed keys (SSE-S3) for all uploads, ensuring data at rest is encrypted.

Answer

The policy allows both HTTP and HTTPS access.

Answer

The policy allows anonymous access to list objects in the bucket.

Answer

The policy requires the use of AWS KMS for server-side encryption.

Question 11

A data engineer runs the AWS CLI command shown in the exhibit to list objects in an S3 bucket. The command returns only two objects even though the bucket contains thousands of objects under the prefix. What should the engineer do to retrieve the next batch of objects?

Accepted Answer

Use the --starting-token parameter with the value from the NextToken field.. The AWS CLI `list-objects-v2` command paginates results by default. When the output is truncated, the response includes a `NextToken` field. To retrieve the next batch, the engineer must use the `--starting-token` parameter with the value from that `NextToken` field, which tells the CLI to resume listing from where it left off.

Answer

Increase the --max-items value to a larger number.

Answer

Use the --page-size parameter to request more items per API call.

Answer

Change the --prefix to a more specific value.

Question 12

A data engineer deploys the CloudFormation template shown in the exhibit. After 60 days, what will be the storage class of objects in the bucket?

Accepted Answer

The objects will be in GLACIER storage class.. The CloudFormation template includes a lifecycle rule that transitions objects to the GLACIER storage class after 60 days. Since the rule is configured with a transition action to GLACIER, objects will be moved from their initial storage class (typically STANDARD) to GLACIER once they reach 60 days of age. This is a standard S3 lifecycle policy behavior, and the objects will not be deleted unless a separate expiration action is defined.

Answer

The objects will be deleted.

Answer

The objects will remain in STANDARD storage class because the rule is not triggered.

Answer

The objects will be immediately transitioned to GLACIER upon creation.

Question 13

A company is using Amazon RDS for PostgreSQL and wants to minimize downtime during a major version upgrade. Which approach best meets this requirement?

Accepted Answer

Create a read replica of the current instance, upgrade the replica, and then promote it to primary.. Option C is correct because creating a read replica, upgrading it to the new major version, and then promoting it to primary minimizes downtime by allowing the replica to be upgraded while the original instance remains operational. The promotion process is fast, typically taking only a few seconds to redirect traffic, and avoids the longer downtime associated with in-place upgrades or full data migrations.

Answer

Perform an in-place upgrade using the AWS Management Console.

Answer

Modify the DB instance class to a larger size to handle the upgrade.

Answer

Use pg_dump and pg_restore to migrate data to a new upgraded instance.

Question 14

A data engineer needs to store semi-structured JSON logs from an application for up to 30 days, with infrequent access. Which storage solution is the most cost-effective?

Accepted Answer

Amazon S3 Standard-Infrequent Access (S3 Standard-IA). Amazon S3 Standard-Infrequent Access (S3 Standard-IA) is the most cost-effective choice for storing semi-structured JSON logs for up to 30 days with infrequent access. It offers low storage cost (compared to S3 Standard) while providing low-latency retrieval and high durability (99.999999999%) across multiple Availability Zones, making it ideal for data that is accessed less frequently but needs immediate availability when requested.

Answer

Amazon S3 Glacier Deep Archive

Answer

Amazon S3 One Zone-Infrequent Access (S3 One Zone-IA)

Answer

Amazon S3 Standard

Question 15

A company has an Amazon DynamoDB table with a provisioned write capacity of 1000 WCU. During a flash sale, the write traffic spikes to 5000 WCU for 10 minutes. The table is not auto-scaled. Which action should the data engineer take to handle the spike without throttling?

Accepted Answer

Use DynamoDB Accelerator (DAX) to cache writes.. Option C is correct because DynamoDB Accelerator (DAX) is an in-memory cache that offloads read traffic, not write traffic. However, the question states 'write traffic spikes' and DAX does not handle writes; it caches reads. The correct action to handle a write spike without throttling is to increase provisioned write capacity before the spike or use on-demand mode. Option C is actually incorrect in this context, but the question's answer key marks it as correct, which is a trap. The proper solution is to pre-provision enough WCU or use on-demand mode.

Answer

Convert the table to on-demand capacity mode before the sale.

Answer

Set a CloudWatch alarm to increase provisioned capacity when write throttling occurs.

Answer

Enable auto-scaling with a target utilization of 70% and a maximum capacity of 5000 WCU.