DEA-C01 Data Store Management Practice Test 23 — 15 Questions

Question 1

The exhibit shows a build log from AWS CodeBuild. The build fails with a permission error when trying to open the downloaded file. What is the most likely cause?

Accepted Answer

The downloaded file has restrictive permissions that the python process cannot read.. The build log shows a permission error when the Python script attempts to open the downloaded file. This typically occurs because the file was downloaded with restrictive permissions (e.g., 600 or 700) that only allow the file owner (likely root) to read it. In AWS CodeBuild, if the Python script runs as a non-root user (or even as root but the file is owned by another user with no read permissions), it cannot access the file. Option C correctly identifies this scenario, while other options are less likely: the S3 bucket policy would affect the download itself, not the open operation; PATH issues relate to command execution, not file reading; encryption would likely produce a different error message.

Answer

The S3 bucket policy denies access to the object.

Answer

The python script is not in the PATH.

Answer

The file is encrypted and cannot be decrypted.

Question 2

A company is running a production database on Amazon RDS for PostgreSQL. The database experiences high read traffic from multiple application servers. Which data store management strategy would reduce the load on the primary database instance?

Accepted Answer

Create an RDS Read Replica in the same region.. Creating an RDS Read Replica in the same region offloads read-heavy traffic from the primary PostgreSQL instance by providing a separate, read-only copy of the database. Application servers can direct SELECT queries to the Read Replica, reducing the primary instance's CPU and I/O load without affecting write performance. This is the most direct and cost-effective strategy for scaling read capacity in Amazon RDS for PostgreSQL.

Answer

Enable DynamoDB Accelerator (DAX) for the database.

Answer

Enable Multi-AZ deployment for automatic failover.

Answer

Use Amazon ElastiCache to cache query results.

Question 3

A data engineer notices that an Amazon Redshift cluster is running low on disk space. The cluster has three nodes of type dc2.large. Which action will increase the available storage capacity?

Accepted Answer

Increase the number of nodes in the cluster.. Amazon Redshift stores data on the local instance store volumes attached to each node in the cluster. With a dc2.large cluster, each node provides approximately 160 GB of SSD storage. Adding nodes increases the total available storage linearly because each new node contributes its local storage to the cluster. Therefore, increasing the number of nodes is the correct way to expand disk capacity.

Answer

Mount an Amazon S3 bucket as a file system to store data.

Answer

Change the volume type to Provisioned IOPS SSD (io1) to increase capacity.

Answer

Enable automatic compression on the tables.

Question 4

A company uses Amazon DynamoDB as a session store for a web application. During peak hours, the application experiences high latency and throttling on the DynamoDB table. The table has a read capacity of 5000 RCU and write capacity of 2000 WCU. The application reads and writes session data using the session ID as the partition key. What is the most cost-effective solution to reduce throttling?

Accepted Answer

Implement DynamoDB Accelerator (DAX) to cache frequent reads.. DynamoDB Accelerator (DAX) provides an in-memory cache that absorbs read-heavy traffic, reducing the load on the underlying DynamoDB table. Since the application reads session data using the session ID as the partition key, DAX can serve frequent reads with microsecond latency, eliminating throttling without requiring a capacity increase. This is the most cost-effective solution because it avoids provisioning additional RCUs for reads that are repetitive and cacheable.

Answer

Enable Auto Scaling on the table to automatically adjust capacity.

Answer

Increase the read capacity units (RCU) and write capacity units (WCU) to 10000 each.

Answer

Enable DynamoDB global tables to distribute read traffic.

Question 5

A data engineer needs to store semi-structured JSON files that are accessed infrequently but must be retrievable within minutes. The data should be stored cost-effectively. Which storage solution meets these requirements?

Accepted Answer

Amazon S3 Standard-Infrequent Access (S3 Standard-IA) storage class.. Amazon S3 Standard-Infrequent Access (S3 Standard-IA) is the correct choice because it is designed for data accessed infrequently but requires rapid retrieval (within milliseconds). It offers lower storage costs than S3 Standard while maintaining low-latency access, meeting the requirement of retrievability within minutes cost-effectively.

Answer

Amazon S3 Glacier Flexible Retrieval storage class.

Answer

Amazon S3 Glacier Deep Archive storage class.

Answer

Amazon S3 Standard storage class.

Question 6

A company uses Amazon Redshift for analytics. The data engineer notices that some queries are slow and the EXPLAIN plan shows a 'Seq Scan' on a large table. Which data store management action would most likely improve query performance?

Accepted Answer

Define appropriate sort keys and distribution styles.. A Seq Scan indicates that Redshift is scanning the entire table because it lacks efficient data organization. Defining appropriate sort keys and distribution styles organizes data on disk and across nodes, enabling Redshift to use zone maps to skip large portions of data and to execute parallel, co-located joins, which directly reduces the need for full table scans.

Answer

Run the ANALYZE command to update table statistics.

Answer

Enable automatic compression on the table.

Answer

Run the VACUUM command to reclaim space.

Question 7

A company stores IoT sensor data in an Amazon S3 bucket. The data is ingested every minute and each object is about 10 KB. The data must be stored for at least 7 years for compliance. Which lifecycle policy configuration minimizes storage costs?

Accepted Answer

Transition to S3 Glacier Deep Archive after 30 days and expire after 2555 days.. S3 Glacier Deep Archive is the lowest-cost storage class for long-term archival data, and transitioning directly after 30 days minimizes costs for 10 KB objects that are accessed infrequently. The 2555-day expiration (7 years) meets the compliance requirement. Other options incur higher costs by using more expensive intermediate tiers or by delaying the transition to the cheapest storage class.

Answer

Transition to S3 One Zone-IA after 30 days, then to S3 Glacier Deep Archive after 365 days, and expire after 2555 days.

Answer

Transition to S3 Glacier Flexible Retrieval after 90 days and expire after 2555 days.

Answer

Transition to S3 Standard-IA after 30 days, then to S3 Glacier Deep Archive after 365 days, and expire after 2555 days.

Question 8

A data engineer is designing a data lake on Amazon S3. The data includes personally identifiable information (PII) that must be encrypted at rest. Which encryption option provides the most control over encryption keys?

Accepted Answer

Server-side encryption with AWS KMS managed keys (SSE-KMS).. SSE-KMS allows you to use AWS Key Management Service (KMS) to manage your encryption keys, providing you with control over key rotation, access policies, and auditing via AWS CloudTrail. This offers more control than SSE-S3 (where AWS manages the keys entirely) and more flexibility than SSE-C (where you manage the keys yourself but lose AWS-managed key rotation and auditing). Client-side encryption (Option A) gives you control but requires you to manage the encryption process and keys outside of S3, which is not a server-side encryption option and adds complexity.

Answer

Client-side encryption using Amazon S3 Encryption Client.

Answer

Server-side encryption with S3 managed keys (SSE-S3).

Answer

Server-side encryption with customer-provided keys (SSE-C).

Question 9

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The primary instance fails, and automatic failover occurs. After failover, the application experiences higher latency. What is the most likely cause?

Accepted Answer

The new primary instance is in a different Availability Zone, increasing network latency.. After a Multi-AZ failover in Amazon RDS for MySQL, the new primary instance is launched in a different Availability Zone (AZ) than the original primary. If the application's compute resources (e.g., EC2 instances) remain in the original AZ, cross-AZ network traffic incurs additional latency due to the physical distance and the need to traverse the AZ boundary, which typically adds 1–2 ms of round-trip time. This increased network latency directly impacts application performance, especially for latency-sensitive queries.

Answer

The read replica is now the primary and cannot handle write traffic.

Answer

The failover process disabled automatic backups.

Answer

The DNS endpoint did not update to point to the new primary.

Question 10

A data engineer is migrating an on-premises Apache HBase workload to Amazon DynamoDB. The HBase table has a row key with composite structure: customer_id (10 chars) + timestamp (10 digits). The access pattern is to query by customer_id and retrieve the latest entries. How should the DynamoDB table be designed to optimize performance?

Accepted Answer

Create a table with partition key = customer_id and sort key = timestamp.. DynamoDB's partition key (customer_id) evenly distributes data across partitions, while the sort key (timestamp) enables efficient range queries using Query with ScanIndexForward=false to retrieve the latest entries. This design directly maps the HBase composite row key pattern to DynamoDB's primary key structure, optimizing for the described access pattern.

Answer

Use Amazon S3 with customer_id as prefix and timestamp as object name.

Answer

Create a table with partition key = concatenated customer_id and timestamp.

Answer

Create a table with partition key = timestamp and sort key = customer_id.

Question 11

A company is designing a disaster recovery strategy for an Amazon RDS for SQL Server database. The database must be recoverable in another AWS region within 15 minutes of a regional outage. Which TWO actions should the data engineer take?

Accepted Answer

Configure automated cross-region snapshots to be copied to the recovery region.. Cross-region snapshots for Amazon RDS are automatically copied to a destination AWS region, enabling you to restore the database in the recovery region from the most recent snapshot. This meets the 15-minute recovery time objective (RTO) when combined with a pre-provisioned DB instance, as the snapshot copy is asynchronous but can be scheduled to occur frequently (e.g., every 5 minutes for SQL Server).

Answer

Enable Multi-AZ deployment on the primary instance.

Answer

Configure automated backups to copy to the recovery region.

Question 12

A data engineer is using Amazon Athena to query data stored in an S3 bucket. The queries are running slowly. Which THREE actions can improve query performance?

Accepted Answer

Partition the data on commonly filtered columns.. Partitioning data on commonly filtered columns (Option A) improves Athena query performance by reducing the amount of data scanned. Athena uses Hive-style partitioning (e.g., `s3://bucket/table/year=2023/month=01/`), and when a query includes a filter on the partition column, Athena prunes partitions and only reads the relevant S3 prefixes. This directly reduces I/O and query cost, as Athena charges per TB of data scanned.

Answer

Convert the data to JSON format for better schema evolution.

Answer

Move the data to S3 Standard-IA storage class.

Question 13

A company is building a data pipeline that ingests streaming data from IoT devices. The data must be stored in a durable, scalable, and cost-effective manner for batch processing. Which TWO AWS services should be used together?

Accepted Answer

Amazon Kinesis Data Streams. Amazon Kinesis Data Streams (B) is the correct ingestion service for streaming IoT data because it provides a durable, scalable, and real-time data streaming platform that can capture and store data records for up to 365 days. Amazon S3 (E) is the correct storage service for batch processing because it offers virtually unlimited durability (99.999999999%), cost-effective tiered storage, and native integration with batch processing frameworks like Amazon EMR and AWS Glue. Together, they form a classic streaming-to-batch pipeline: Kinesis ingests and buffers the streaming data, which is then persisted in S3 for downstream batch analytics.

Answer

Amazon ElastiCache

Answer

Amazon Redshift

Answer

Amazon DynamoDB

Question 14

A data engineer applies the following IAM policy to an IAM user:

```json
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::example-bucket/*",
      "Condition": {
        "StringEquals": {
          "s3:x-amz-server-side-encryption": "AES256"
        }
      }
    }
  ]
}
```

The user attempts to download an object from the bucket 'example-bucket' that is encrypted with SSE-S3 (AES256). Will the request succeed?

Accepted Answer

No, because the policy requires the encryption to be specified in the request.. The IAM policy includes a condition that requires the request to include the `x-amz-server-side-encryption` header with value `AES256`. Even though the object is encrypted with SSE-S3, the policy condition evaluates the request headers, not the object's encryption state. Since the user does not specify the encryption header in the download request, the condition fails, and the request is denied.

Answer

Yes, but only if the user also has s3:ListBucket permission.

Answer

Yes, because the object is encrypted with SSE-S3 which uses AES256.

Answer

No, because the policy does not allow the s3:GetObject action for encrypted objects.

Question 15

An application uses the 'orders' DynamoDB table with the schema and provisioned throughput shown in the exhibit. The application frequently queries by customer_id (range key) without specifying the order_id (partition key). What is the most likely impact on performance?

Accepted Answer

Queries will require a full table scan, consuming significant read capacity.. The application queries by customer_id (the sort key) without specifying order_id (the partition key). In DynamoDB, a Query operation requires the partition key to be specified; without it, the only way to retrieve items is a full table Scan, which reads every item in the table. This consumes read capacity proportional to the entire table size, leading to high latency and cost.

Answer

Queries will be throttled because the table does not have a global secondary index.

Answer

Queries will be fast because the sort key is indexed.

Answer

Queries will cause hot partitions on the table.