DEA-C01 Data Store Management Practice Test 6 — 15 Questions

Question 1

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?

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

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

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Use DynamoDB as the Hive metastore to improve metadata access

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Use Amazon Redshift Spectrum to query the data directly from S3

Question 2

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

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Amazon S3 Glacier Deep Archive

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Amazon EBS gp3 volumes attached to an EC2 instance

Question 3

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

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Enable auto scaling for the table with a higher maximum capacity

Question 4

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

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Amazon EBS

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Amazon DynamoDB

Question 5

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

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Automated backups with a retention period of 30 days

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Read replicas in a different Region

Question 6

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.. 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 7

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.

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

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Change the --prefix to a more specific value.

Question 8

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 with a transition action to the GLACIER storage class after 60 days from object creation. Since the rule is properly configured and no expiration action is defined, objects will be moved from STANDARD to GLACIER at day 60. This is standard S3 lifecycle behavior, and objects are not deleted unless a separate expiration rule is set.

Answer

The objects will be deleted.

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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 9

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.. 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.

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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 10

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

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

Answer

Amazon S3 Standard

Question 11

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

Convert the table to on-demand capacity mode before the sale.. The table is currently provisioned with 1000 WCU and cannot handle a spike to 5000 WCU. Converting to on-demand mode before the sale allows DynamoDB to automatically handle varying traffic without throttling, as on-demand capacity scales instantly to meet demand. Option D (auto-scaling) might not react quickly enough for a short 10-minute spike, and the table is not currently auto-scaled. Option C is incorrect because DAX is a read cache and does not buffer or improve write capacity. Option B is reactive and would not prevent initial throttling.

Answer

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

Answer

Use DynamoDB Accelerator (DAX) to cache writes.

Answer

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

Question 12

A data engineer is designing a data lake on Amazon S3 and needs to ensure that objects are automatically encrypted at rest using server-side encryption with AWS KMS. Which bucket policy statement achieves this?

Accepted Answer

Deny PutObject requests where the x-amz-server-side-encryption header is not set to aws:kms.. It enforces server-side encryption with AWS KMS (SSE-KMS) by denying any PutObject request that does not include the `x-amz-server-side-encryption` header set to `aws:kms`. This bucket policy ensures that all objects written to the S3 bucket are automatically encrypted at rest using AWS KMS, meeting the requirement for mandatory encryption with a specific key management service.

Answer

Deny PutObject requests that do not include the x-amz-server-side-encryption header.

Answer

Deny PutObject requests where the x-amz-server-side-encryption header is not set to AES256.

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Allow PutObject requests only if the x-amz-server-side-encryption header is set to AES256.

Question 13

A company uses Amazon Redshift for its data warehouse. The data engineer notices that queries are slow on a large table that is frequently filtered on a column 'transaction_date'. Which optimization technique best improves query performance?

Accepted Answer

Set the sort key to 'transaction_date'.. Setting the sort key to 'transaction_date' organizes the table data physically by that column, which allows Redshift to use zone maps to skip blocks that don't match query filters. This dramatically reduces the amount of data scanned for range-restricted queries on 'transaction_date', improving query performance.

Answer

Apply compression encoding to 'transaction_date'.

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Set the distribution key to 'transaction_date'.

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Run VACUUM on the table.

Question 14

A data engineer is migrating an on-premises MongoDB database to Amazon DocumentDB. Which migration strategy minimizes downtime?

Accepted Answer

Use AWS DMS with full load and ongoing replication from MongoDB to DocumentDB.. AWS DMS with full load and ongoing replication (change data capture) minimizes downtime by continuously synchronizing changes from the source MongoDB to the target DocumentDB after the initial full load, allowing a cutover with only a brief pause. This is the only option that supports near-zero downtime migration for live databases.

Answer

Take a snapshot of the MongoDB database and restore it to DocumentDB.

Answer

Use AWS Database Migration Service (AWS DMS) with full load only.

Answer

Export data using mongodump and import using mongorestore.

Question 15

A company needs to store files that are accessed by multiple EC2 instances in a VPC. The files must be concurrently accessible and durable. Which storage solution should the data engineer choose?

Accepted Answer

Amazon Elastic File System (Amazon EFS). Amazon EFS provides a fully managed, scalable, and elastic NFS file system that can be concurrently accessed by multiple EC2 instances across multiple Availability Zones. It is designed for high durability (11 nines of durability) and automatically replicates data across multiple AZs within a region, meeting the requirements for concurrent access and durability.

Answer

Amazon EC2 instance store

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Amazon Simple Storage Service (Amazon S3)

Answer

Amazon Elastic Block Store (Amazon EBS)