DEA-C01 Data Store Management Practice Test 27 — 15 Questions

Question 1

A data engineer needs to store semi-structured JSON data from IoT devices. The data is written frequently and read occasionally. Which AWS service is MOST cost-effective for this use case?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the most cost-effective choice because it is a fully managed NoSQL key-value and document database that natively supports semi-structured JSON data, offers single-digit millisecond latency for frequent writes, and provides a pay-per-request pricing model ideal for workloads with occasional reads. Its on-demand capacity mode automatically scales to handle high write throughput without provisioning, making it cheaper than provisioned alternatives for spiky or unpredictable IoT ingestion patterns.

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Answer

Amazon Redshift

Question 2

A company is using Amazon S3 to store sensitive customer data. The security team requires that all data be encrypted in transit and at rest. Additionally, they want to prevent any accidental public access. Which combination of actions should the data engineer take?

Accepted Answer

Enable default encryption with SSE-S3, enforce HTTPS only via bucket policy, and enable S3 Block Public Access.. Enabling default encryption with SSE-S3 ensures data is encrypted at rest automatically, enforcing HTTPS only via bucket policy ensures encryption in transit by rejecting HTTP requests, and enabling S3 Block Public Access prevents any accidental public exposure regardless of bucket policies or ACLs. This combination satisfies all security requirements: encryption in transit, encryption at rest, and prevention of public access.

Answer

Enable default encryption with SSE-KMS, allow both HTTP and HTTPS, and set bucket ACLs to private.

Answer

Use client-side encryption, enforce HTTPS via bucket policy, and enable S3 Block Public Access.

Answer

Enable default encryption with SSE-S3, allow HTTP and HTTPS, and use bucket ACLs to block public access.

Question 3

A data engineer is designing a data store for a real-time leaderboard application that requires sub-millisecond read and write latency. The leaderboard stores scores for millions of users and needs to be sorted by score. Which AWS service should the engineer use?

Accepted Answer

Amazon ElastiCache for Redis with a sorted set. Amazon ElastiCache for Redis provides a sorted set data structure (ZADD/ZRANGE commands) that maintains elements ordered by a numeric score with O(log N) complexity for both writes and reads, enabling sub-millisecond latency for real-time leaderboard updates and queries. This is the only option purpose-built for in-memory, sorted, real-time leaderboards at scale.

Answer

Amazon RDS for PostgreSQL with an index on score

Answer

Amazon DynamoDB with a global secondary index on score

Answer

Amazon Neptune with a graph model

Question 4

A data engineer needs to store archival data that is rarely accessed but must be retained for 7 years. The data should be retrievable within 12 hours. Which Amazon S3 storage class is MOST cost-effective?

Accepted Answer

S3 Glacier Deep Archive. S3 Glacier Deep Archive is the most cost-effective storage class for archival data that is rarely accessed and requires a 7-year retention period, with retrieval times up to 12 hours. It offers the lowest storage cost among S3 classes, making it ideal for long-term retention of data that does not need immediate access.

Answer

S3 Intelligent-Tiering

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S3 Glacier Flexible Retrieval

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S3 Standard

Question 5

Which THREE factors should a data engineer consider when choosing between Amazon RDS and Amazon DynamoDB for a new application? (Choose three.)

Accepted Answer

Whether the workload requires serverless scaling.. Amazon RDS is a relational database service that requires provisioning and managing server capacity, while DynamoDB is a fully managed NoSQL key-value and document database that supports serverless scaling. Option A is correct because DynamoDB can automatically scale throughput capacity up or down based on traffic patterns, making it suitable for unpredictable workloads, whereas RDS requires manual scaling or the use of Auto Scaling with predefined policies.

Answer

Whether the data must be encrypted at rest by default.

Answer

Whether the application requires VPC isolation.

Question 6

Which TWO methods can be used to enforce least-privilege access to an Amazon S3 bucket? (Choose two.)

Accepted Answer

Use IAM policies to grant specific permissions to users and roles.. IAM policies allow you to grant granular, specific permissions to individual users and roles, adhering to the principle of least privilege by explicitly allowing only the actions required. This avoids granting broad or default permissions, ensuring that each identity has only the access necessary for its function.

Answer

Set bucket ACLs to allow full control to the bucket owner only.

Answer

Configure a VPC endpoint to restrict access to the bucket.

Answer

Generate pre-signed URLs for all access.

Question 7

Refer to the exhibit. A data engineer applies this bucket policy to an S3 bucket. A user within the 10.0.0.0/24 IP range attempts to upload an object to the bucket using an HTTP (non-HTTPS) request. What is the outcome?

Accepted Answer

The upload fails because the request is not using HTTPS.. The bucket policy includes a condition `aws:SecureTransport` set to `false`, which explicitly denies any request that does not use HTTPS. Since the user is making an HTTP (non-HTTPS) request, the Deny statement overrides any Allow statement, causing the upload to fail. The correct answer is D.

Answer

The upload succeeds because the Allow statement grants permission.

Answer

The upload succeeds because the user's IP is allowed.

Answer

The upload fails because the user's IP is not in the allowed range for PutObject.

Question 8

Refer to the exhibit. A data engineer runs the above CLI command and sees the output. The security team requires that the RDS instance not be accessible from the internet. Which change should the engineer make?

Accepted Answer

Modify the DB instance to set PubliclyAccessible to false.. Setting the `PubliclyAccessible` attribute to `false` ensures that the RDS instance is not assigned a public IP address and is not reachable from the internet. This directly satisfies the security team's requirement, as the instance will only be accessible from within the VPC. The CLI command shown modifies the DB instance, and this parameter is the standard AWS mechanism to control internet accessibility for RDS.

Answer

Change the storage type to io1 for better performance.

Answer

Enable Multi-AZ deployment to improve security.

Answer

Update the VPC security group to deny inbound traffic from 0.0.0.0/0.

Question 9

Refer to the exhibit. A data engineer creates an Amazon Redshift table with the above DDL. The engineer runs a query to find all orders for a specific customer within a date range. Which statement about query performance is correct?

Accepted Answer

The query will benefit from both the distribution key and the sort key to minimize data scanned.. The DDL defines customer_id as the distribution key and order_date as the sort key. When the query filters on both customer_id (distribution key) and order_date (sort key), Redshift can use partition pruning via the sort key to skip blocks that don't match the date range, and the distribution key ensures that data for the same customer is co-located on the same node slice, minimizing data movement. This combination reduces the amount of data scanned and improves query performance.

Answer

The query will be inefficient because the distribution key is not the same as the sort key.

Answer

The table should use DISTSTYLE EVEN to improve performance.

Answer

The sort key will not help because the query filters on customer_id first.

Question 10

A company uses an Amazon RDS for MySQL DB instance with Multi-AZ deployment. The primary DB instance fails unexpectedly. What happens to the database endpoint?

Accepted Answer

The existing endpoint continues to work and automatically points to the standby DB instance.. In a Multi-AZ RDS deployment, the DNS endpoint remains unchanged during a failover. When the primary DB instance fails, Amazon RDS automatically updates the DNS record to point to the standby instance in the other Availability Zone. This ensures the application can continue using the same endpoint without any manual intervention, providing high availability.

Answer

A new endpoint is created for the standby and the application must use the new endpoint.

Answer

The database becomes unavailable until the primary is restored from a snapshot.

Answer

The existing endpoint is deleted and a new endpoint is provided after manual DNS update.

Question 11

A data engineer is designing a data lake on Amazon S3. Data is ingested from multiple sources in JSON format. The engineer needs to optimize query performance for Amazon Athena while minimizing storage costs. Which storage strategy should the engineer use?

Accepted Answer

Convert data to Parquet format and partition by date.. Parquet is a columnar storage format that significantly reduces data scan volume in Amazon Athena, which charges per byte scanned. Partitioning by date further limits the data scanned to only relevant partitions, optimizing both query performance and cost. JSON and CSV are row-based formats that require full scans, and Glacier is unsuitable for interactive querying.

Answer

Store data as CSV files in a single S3 bucket without prefixes.

Answer

Store data as JSON files in a single prefix without partitioning.

Answer

Store compressed JSON files in Amazon S3 Glacier.

Question 12

A company uses Amazon DynamoDB with on-demand capacity for a gaming application that experiences unpredictable traffic spikes. The application reads the same set of 'hot' items frequently. Users report high latency during peak hours. Which action would MOST effectively reduce read latency for the hot items?

Accepted Answer

Enable DynamoDB Accelerator (DAX) for the table.. DynamoDB Accelerator (DAX) is an in-memory cache that sits between the application and DynamoDB, providing microsecond read latency for frequently accessed items. Since the application reads the same set of 'hot' items repeatedly, DAX can serve these reads from its cache, bypassing the storage layer and reducing latency during traffic spikes without requiring any table schema changes.

Answer

Switch to provisioned capacity with auto-scaling.

Answer

Increase the read capacity units for the table.

Answer

Enable DynamoDB Global Tables for multi-region replication.

Question 13

A data engineer is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB in size. The engineer needs to minimize downtime. Which AWS service should be used for the migration?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is the correct choice because it supports continuous replication (change data capture) from an on-premises PostgreSQL source to Amazon RDS for PostgreSQL, enabling near-zero downtime migration. DMS can handle a 2 TB database by using a large replication instance and tuning task settings, and it automatically converts the source schema to the target RDS engine.

Answer

AWS Data Pipeline

Answer

AWS Snowball

Answer

Amazon S3

Question 14

A company stores sensitive customer data in an Amazon S3 bucket. The security team requires that all data be encrypted at rest using a key that is automatically rotated every year. Which encryption solution should the data engineer use?

Accepted Answer

SSE-KMS with a customer managed key. SSE-KMS with a customer managed key is correct because it allows you to use an AWS KMS key that you control, enabling automatic annual key rotation via the KMS key rotation feature. This satisfies the security team's requirement for encryption at rest with a key that is automatically rotated every year, while maintaining control over the key lifecycle.

Answer

SSE-S3

Answer

SSE-C

Answer

Client-side encryption

Question 15

A company runs a production Amazon Redshift cluster with a 5-node ra3.4xlarge configuration. The data engineer observes that write operations are failing with 'Disk Full' errors on some nodes. The cluster has not reached its total capacity. What should the engineer do to resolve this issue?

Accepted Answer

Recreate the table with a different distribution style to avoid data skew.. The 'Disk Full' errors on some nodes, despite the cluster not reaching total capacity, indicate data skew caused by an inappropriate distribution style. Recreating the table with a different distribution style (e.g., DISTKEY on a high-cardinality column or DISTSTYLE EVEN) redistributes data evenly across all nodes, eliminating the hot spots that exhaust local disk space.

Answer

Change the sort keys to distribute data evenly.

Answer

Enable compression on all tables.

Answer

Add more nodes to the cluster.