DEA-C01 Data Store Management Practice Test 24 — 15 Questions

Question 1

A data engineer runs the above SQL commands on an Amazon Redshift cluster. The table 'users' is created with DISTSTYLE EVEN. What is the effect of the DISTSTYLE EVEN on query performance?

Accepted Answer

It ensures data is evenly distributed across all nodes to prevent data skew.. DISTSTYLE EVEN in Amazon Redshift distributes rows across all nodes in a round-robin fashion, ensuring each node holds approximately the same amount of data. This prevents data skew, which can cause some nodes to become bottlenecks, and improves overall query performance for workloads that do not benefit from key-based distribution. It is the correct choice because it directly addresses the goal of balanced data distribution.

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It stores all data on a single node for fast local queries.

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It reduces data movement during queries by co-locating data based on user_id.

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It improves join performance when joining on user_id.

Question 2

A company is using an Amazon RDS for MySQL database for an e-commerce application. During a sales event, the database experiences high read traffic, causing slow query performance. The company wants to reduce the read load on the primary database without changing the application code. Which solution meets these requirements?

Accepted Answer

Create an Amazon RDS read replica and direct read traffic to it.. An Amazon RDS read replica is a read-only copy of the primary database that can offload read traffic without requiring any application code changes. By directing read queries to the replica, the primary database's load is reduced, improving performance during high-read events. This solution is specifically designed for read-heavy workloads and integrates seamlessly with existing MySQL connections.

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Enable Multi-AZ on the RDS instance.

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Increase the instance size of the RDS database.

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Deploy Amazon ElastiCache to cache query results.

Question 3

A data engineer needs to store semi-structured JSON data that is accessed infrequently but must be retrievable within minutes when needed. The data will be stored for 7 years for compliance. Which storage solution is MOST cost-effective?

Accepted Answer

Amazon S3 Glacier Deep Archive. Amazon S3 Glacier Deep Archive is the most cost-effective storage class for data that is accessed infrequently, requires retrieval within minutes (using expedited retrieval), and must be stored for 7 years for compliance. It offers the lowest storage cost among S3 classes, making it ideal for long-term archival of semi-structured JSON data with minimal access needs.

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Amazon S3 One Zone-Infrequent Access

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Amazon S3 Standard

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Amazon S3 Intelligent-Tiering

Question 4

A company uses Amazon DynamoDB as the primary data store for a gaming application. The application experiences sudden spikes in traffic. The data engineer notices that write requests are throttled during peak times. The partition keys are well-distributed. What should the data engineer do to reduce throttling?

Accepted Answer

Configure DynamoDB auto scaling to adjust write capacity automatically.. DynamoDB auto scaling allows the table to automatically adjust its provisioned write capacity based on actual traffic patterns, preventing throttling during sudden spikes without manual intervention. Since the partition keys are already well-distributed, throttling is likely due to insufficient write capacity units, which auto scaling can dynamically increase.

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Use DynamoDB global tables to distribute writes across regions.

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Increase the number of partition keys to improve write distribution.

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Enable DynamoDB Accelerator (DAX) to cache write operations.

Question 5

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.

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AWS Glue

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AWS Snowball

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Amazon S3 Transfer Acceleration

Question 6

A company uses Amazon Redshift for data warehousing. The data engineer notices that query performance has degraded over time. The tables are frequently updated with new data, and the data engineer suspects that the distribution style is causing data skew. Which distribution style should the data engineer use to minimize data skew?

Accepted Answer

EVEN distribution. EVEN distribution (D) distributes rows across all slices in a round-robin fashion, ensuring each slice holds approximately the same number of rows. This eliminates data skew caused by uneven distribution keys, which is the suspected issue when query performance degrades over time with frequent updates. By avoiding any dependency on column values, EVEN distribution guarantees balanced data distribution regardless of data characteristics.

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KEY distribution on a column with high cardinality

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AUTO distribution

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ALL distribution

Question 7

A company is designing a data lake on Amazon S3. The data includes personal identifiable information (PII). The data engineer must ensure that only authorized users can access the data, and that access is logged for auditing. Which combination of services should the data engineer use?

Accepted Answer

S3 bucket policies with IAM policies and AWS CloudTrail with data events. S3 bucket policies combined with IAM policies provide fine-grained access control to restrict who can access the data, while AWS CloudTrail with data events logs every S3 object-level operation (e.g., GetObject, PutObject) for auditing. This combination directly meets the requirements of authorized access and logging for PII data.

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Amazon S3 access points and VPC endpoints

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Amazon Macie to discover PII and S3 Object Lock to prevent deletion

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AWS KMS to encrypt data and AWS CloudTrail to log access

Question 8

A company is storing large amounts of log data in Amazon S3. The data is accessed frequently for the first 30 days, then rarely after that. The company wants to automatically transition the data to a lower-cost storage class after 30 days. Which S3 feature should the data engineer use?

Accepted Answer

S3 Lifecycle policies. S3 Lifecycle policies allow you to define rules that automatically transition objects between storage classes based on age or other criteria. In this scenario, a lifecycle rule can be configured to transition objects from S3 Standard to a lower-cost class like S3 Glacier Deep Archive after 30 days, directly meeting the requirement for automated cost optimization.

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S3 Intelligent-Tiering

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S3 Cross-Region Replication

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S3 Batch Operations

Question 9

A company is using Amazon DynamoDB to store session data for a web application. The data engineer needs to ensure that the data is encrypted at rest. Which action should the data engineer take?

Accepted Answer

Ensure encryption at rest is enabled on the DynamoDB table (default).. DynamoDB tables are encrypted at rest by default using AWS Key Management Service (KMS) with an AWS owned key. The data engineer does not need to take any additional action to enable encryption at rest, as it is automatically enabled for all new DynamoDB tables. This ensures that all data stored on disk, including the table's primary key, local secondary indexes, and global secondary indexes, is encrypted before being written to SSDs in AWS data centers.

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Enable encryption at rest on the DynamoDB Accelerator (DAX) cluster.

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Use client-side encryption before writing to DynamoDB.

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Enable DynamoDB Time to Live (TTL) to encrypt data.

Question 10

A company is using Amazon S3 to store sensitive data. The security team requires that all data be encrypted at rest using a customer-managed AWS KMS key. The data engineer must ensure that only a specific IAM role can decrypt the data. Which policy should the data engineer attach to the KMS key?

Accepted Answer

A KMS key policy that allows the IAM role to perform kms:Decrypt. KMS key policies are the primary mechanism for controlling access to a customer-managed KMS key. By specifying the IAM role as a principal in the key policy and granting kms:Decrypt, you ensure that only that role can decrypt data encrypted with this key, regardless of any IAM policies that might otherwise allow broader access.

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An IAM user policy that allows kms:Decrypt for the specific key

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An IAM policy attached to the role that allows kms:Decrypt

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An S3 bucket policy that denies access unless encryption is used

Question 11

Which TWO statements are true about Amazon Redshift distribution styles? (Choose TWO.)

Accepted Answer

ALL distribution copies the entire table to every node.. The ALL distribution style in Amazon Redshift copies the entire table to every node in the cluster. This is ideal for small, slowly changing dimension tables (like date or location tables) that need to be joined with large fact tables, as it eliminates the need to redistribute data across nodes during query execution.

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KEY distribution is always the best choice to minimize data skew.

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AUTO distribution always selects EVEN distribution.

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Redshift automatically assigns a ROUND ROBIN distribution style by default.

Question 12

Which THREE actions can help improve read performance in Amazon DynamoDB? (Choose THREE.)

Accepted Answer

Use parallel scans to distribute read load across partitions.. Parallel scans in DynamoDB can improve read performance by dividing a scan operation into multiple segments that are processed concurrently across partitions. This reduces the overall latency of the scan by leveraging the distributed nature of DynamoDB's storage, though it consumes more read capacity units (RCUs) due to the parallel execution.

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Use DynamoDB global tables to replicate data.

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Use strongly consistent reads for all queries.

Question 13

Which TWO are benefits of using Amazon S3 Object Lock? (Choose TWO.)

Accepted Answer

Helps meet regulatory requirements for write-once-read-many (WORM) storage.. Amazon S3 Object Lock helps meet regulatory requirements for write-once-read-many (WORM) storage by allowing you to set retention periods and legal holds on objects. This ensures that data cannot be deleted or overwritten for a specified duration, which is a common requirement for compliance frameworks such as SEC Rule 17a-4 or FINRA.

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Encrypts objects at rest using AWS KMS.

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Automatically transitions objects to lower-cost storage classes.

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Enables automatic versioning of objects.

Question 14

A data engineer is analyzing a DynamoDB table for a session management application. The table currently has 10,000 items and is 1 MB in size. The application expects 1,000 writes per second during peak hours. What should the data engineer do to accommodate the write workload?

Accepted Answer

Increase the write capacity units (WCU) for the table.. DynamoDB write capacity is provisioned in Write Capacity Units (WCUs), and the table's current WCU setting is insufficient for 1,000 writes per second. Increasing the WCU ensures the table can handle the peak write throughput without throttling, as each WCU supports one write per second for items up to 1 KB. The table size (1 MB) and item count (10,000) are irrelevant to throughput capacity.

Answer

Reduce the item size to improve write performance.

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Use global tables to distribute writes across regions.

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Enable DynamoDB Accelerator (DAX) to offload writes.

Question 15

A data engineer is reviewing an IAM policy that controls access to an S3 bucket. The policy is attached to a user group. The policy includes a condition that explicitly requires server-side encryption with SSE-S3 for all GetObject requests. The engineer notices that users are unable to download objects from the bucket. What is the likely cause?

Accepted Answer

The objects are encrypted using SSE-KMS, not SSE-S3.. The IAM policy includes a condition that allows downloads only if the object is encrypted with SSE-S3. However, the objects in the bucket are encrypted using SSE-KMS, which does not satisfy the condition. As a result, the s3:GetObject request is denied. This is a common scenario where a specific encryption condition in the policy blocks access when the actual encryption method differs. The other options are less likely: attaching the policy to a user group is valid and does not cause download issues; an incorrect bucket ARN would affect all operations, not just downloads; and missing s3:GetObject would be a straightforward policy error that would be easily identified.

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The policy is attached to a user group instead of an IAM role.

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The policy does not specify the correct bucket ARN.

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The policy does not allow the s3:GetObject action.