DEA-C01 Data Store Management Practice Test 10 — 15 Questions

Question 1

A data engineer needs to store semi-structured JSON transaction logs for analytics. The logs are written once and rarely accessed. The storage must be cost-effective. Which AWS service should be used?

Accepted Answer

Amazon S3. Amazon S3 is the correct choice because it provides highly durable, cost-effective object storage ideal for semi-structured JSON transaction logs that are written once and rarely accessed. S3's lifecycle policies can automatically transition such infrequently accessed data to S3 Glacier or S3 Glacier Deep Archive for even lower storage costs, making it the most economical option for this use case.

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Amazon DynamoDB

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Amazon RDS

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Amazon Redshift

Question 2

A company uses Amazon Redshift for a data warehouse. They notice that queries are slow due to heavy data skew. Which optimization technique should be applied first?

Accepted Answer

Set an appropriate distribution style. Data skew occurs when rows are distributed unevenly across Redshift slices, causing some nodes to process far more data than others. Setting an appropriate distribution style (e.g., KEY, EVEN, or ALL) redistributes the data to balance the workload, directly addressing the root cause of the slowness. This is the first optimization to apply because skew is a fundamental distribution issue that other tuning steps cannot fix.

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Configure workload management (WLM) queues

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Define sort keys on frequently filtered columns

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Apply compression encodings to columns

Question 3

A data engineer is designing a data lake on Amazon S3. The data includes sensitive customer information that must be encrypted at rest. Which combination of actions meets this requirement with minimal operational overhead?

Accepted Answer

Enable default encryption on the S3 bucket using SSE-S3. SSE-S3 provides server-side encryption with Amazon S3-managed keys, which encrypts data at rest with minimal operational overhead because AWS handles key management, rotation, and encryption/decryption transparently. Enabling default encryption on the S3 bucket ensures that all objects written to the bucket are automatically encrypted without requiring any client-side changes or additional code, meeting the requirement with the least administrative effort.

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Encrypt objects client-side before uploading

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Use an S3 bucket policy to deny writes without encryption

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Use an S3 Lifecycle policy to transition to Glacier

Question 4

A company has a DynamoDB table with a partition key of 'user_id' and a sort key of 'timestamp'. They need to query all items for a user within a date range. Which query operation should be used?

Accepted Answer

Query with KeyConditionExpression on partition key and sort key. The Query operation in DynamoDB is designed to retrieve items based on a specific partition key and an optional sort key condition. Since the table has a partition key of 'user_id' and a sort key of 'timestamp', using Query with a KeyConditionExpression that filters on the partition key (user_id) and a range condition on the sort key (timestamp) is the most efficient and correct approach to get all items for a user within a date range.

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BatchGetItem with multiple keys

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GetItem with both partition and sort key

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Scan with FilterExpression

Question 5

A data engineer needs to store streaming data from IoT devices for real-time analytics. The data has a fixed schema and requires low-latency queries. Which AWS service should be used?

Accepted Answer

Amazon Timestream. Amazon Timestream is a time-series database purpose-built for IoT and operational applications that generate large volumes of time-stamped data. It automatically manages data retention and storage tiers (memory and magnetic) to provide fast query performance for recent data and cost-effective storage for historical data, making it ideal for real-time analytics on streaming IoT data with a fixed schema.

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Amazon DynamoDB

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Amazon Redshift

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Amazon S3

Question 6

A company stores financial data in Amazon RDS for MySQL. They need to retain backups for 7 years to meet compliance. Which backup strategy meets this requirement?

Accepted Answer

Use the AWS Backup service with a 7-year retention policy. AWS Backup is the correct service for long-term retention of RDS snapshots beyond the 35-day limit of automated backups. It allows you to create backup plans with retention policies up to 100 years, making it suitable for the 7-year compliance requirement. Manual snapshots can also be retained indefinitely, but AWS Backup provides centralized management and lifecycle policies.

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Use read replicas to retain data

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Take daily manual snapshots and delete after 7 years

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Enable automated backups with a retention period of 7 years

Question 7

A data engineer is designing a multi-region disaster recovery solution for Amazon RDS for PostgreSQL. The primary region must have a standby in a different Availability Zone, and the secondary region must have a readable replica that can be promoted in case of failure. Which configuration meets these requirements?

Accepted Answer

Enable Multi-AZ in the primary region and create a cross-region read replica. It meets both requirements: Multi-AZ in the primary region provides a synchronous standby in a different Availability Zone for high availability, and a cross-region read replica in the secondary region provides an asynchronous, readable copy that can be promoted to a standalone primary during a regional failure. This combination ensures both intra-region fault tolerance and inter-region disaster recovery.

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Use a single-AZ primary and enable automatic backups

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Use a single-AZ primary and create a cross-region read replica

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Enable Multi-AZ in both primary and secondary regions

Question 8

A company stores log files in Amazon S3. They want to automatically move logs older than 90 days to S3 Glacier Deep Archive to reduce costs. Which S3 feature should be used?

Accepted Answer

S3 Lifecycle configuration. S3 Lifecycle configuration allows you to define rules that automatically transition objects to colder storage classes, such as S3 Glacier Deep Archive, based on age. By setting a rule to move objects older than 90 days to S3 Glacier Deep Archive, you reduce storage costs without manual intervention. This is the correct feature for automating tier-based data lifecycle management.

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S3 Intelligent-Tiering

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S3 Replication

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S3 Object Lock

Question 9

Which TWO actions can help optimize Amazon S3 storage costs for a data lake? (Choose two.)

Accepted Answer

Use S3 Intelligent-Tiering for unpredictable access patterns. S3 Intelligent-Tiering automatically moves objects between two access tiers (frequent and infrequent) when access patterns change, with no retrieval fees and a small monthly monitoring fee. This is ideal for a data lake where access patterns are unpredictable, as it optimizes costs without requiring manual lifecycle rule adjustments.

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Enable S3 Replication to another region

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Use S3 Select to retrieve only needed data

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Enable S3 Transfer Acceleration

Question 10

Which THREE considerations are important when designing a DynamoDB table for high-traffic gaming leaderboards? (Choose three.)

Accepted Answer

Enable DynamoDB Accelerator (DAX) for low-latency reads. DynamoDB Accelerator (DAX) provides in-memory caching for DynamoDB tables, reducing read latency from single-digit milliseconds to microseconds. For high-traffic gaming leaderboards, where millions of players query scores concurrently, DAX offloads read traffic from the main table, preventing throttling and ensuring consistent low-latency responses for the most frequently accessed data.

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Use strongly consistent reads for all queries

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Enable DynamoDB Streams for real-time updates

Question 11

Which TWO statements about Amazon Redshift data distribution are correct? (Choose two.)

Accepted Answer

KEY distribution places rows with the same distribution key on the same slice. In Amazon Redshift, KEY distribution places all rows with the same distribution key value on the same slice (compute node segment). This ensures that join operations on the distribution key are collocated, reducing data movement across the network and improving query performance.

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DISTSTYLE is a distribution style option

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AUTO distribution always chooses EVEN

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ALL distribution distributes data across all slices

Question 12

Refer to the exhibit. An IAM policy is attached to a user. The user cannot upload objects to the S3 bucket 'example-bucket' using the AWS CLI. What is the most likely cause?

Accepted Answer

The user is not using HTTPS for API calls. The IAM policy explicitly denies all actions unless the request uses HTTPS (via the `aws:SecureTransport` condition key). Since the AWS CLI by default can use HTTP if not explicitly configured to use HTTPS, the user's upload attempt fails. The `s3:PutObject` action is allowed in the policy, but the condition block overrides that permission when the request is not made over HTTPS.

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The policy does not allow s3:PutObject

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The user is not in the same AWS region

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The resource ARN does not include the bucket itself

Question 13

Refer to the exhibit. A data engineer ran the CLI command to check the configuration of an RDS instance named 'mydb'. Which statement accurately describes the current configuration?

Accepted Answer

The database is a Single-AZ deployment and is not a read replica. The CLI command output shows 'DBInstanceStatus: available' and 'MultiAZ: False', indicating the database is running as a Single-AZ deployment. Additionally, the absence of a 'SourceDBInstanceIdentifier' field confirms it is not a read replica. The 'ReadReplicaSourceDBInstanceIdentifier' is not present, which would be required if it were a read replica.

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The database is in the 'stopped' state

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The database is a read replica of another instance

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The database is a Multi-AZ deployment

Question 14

Refer to the exhibit. A DynamoDB table 'Orders' has a GSI 'CustomerDateIndex'. A developer tries to query the GSI for all orders of a customer between two dates. The query fails. What is the most likely reason?

Accepted Answer

The query uses a date format that is not lexicographically sortable as a string. DynamoDB's Query operation requires the sort key to be lexicographically sortable when using comparison operators like BETWEEN. If the 'order_date' attribute is stored as a non-lexicographically sortable string format (e.g., 'MM-DD-YYYY' instead of 'YYYY-MM-DD'), the BETWEEN condition will fail to return correct results or may throw an error. The GSI's sort key must be in a format that supports string comparison for range queries to work properly.

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The GSI does not include 'order_id' in the key schema

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The 'customer_id' attribute is not a partition key in the GSI

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The 'order_date' attribute is not a sort key in the GSI

Question 15

A company is using Amazon S3 to store critical data and needs to ensure that objects are automatically transitioned to S3 Glacier Deep Archive after 180 days to reduce costs. Which S3 lifecycle action should be configured?

Accepted Answer

Transition. The S3 lifecycle 'Transition' action is specifically designed to move objects between storage classes after a specified number of days. To reduce costs by moving objects to S3 Glacier Deep Archive after 180 days, you configure a lifecycle rule with a Transition action that targets the 'DEEP_ARCHIVE' storage class at the 180-day mark.

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Expiration

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AbortIncompleteMultipartUpload

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NoncurrentVersionTransition