DEA-C01 Data Store Management Practice Test 31 — 15 Questions

Question 1

A company has an Amazon RDS for MySQL database that is experiencing performance issues due to a large number of read requests. The application is read-heavy and can tolerate eventually consistent reads. Which action will reduce the load on the primary database with the least operational overhead?

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

Accepted Answer

Create a read replica in the same region. Creating a read replica in the same region offloads read traffic from the primary RDS instance to a read-only copy, which directly addresses the read-heavy workload. Since the application can tolerate eventually consistent reads, the slight replication lag is acceptable, and this solution requires minimal operational overhead—just a few clicks in the AWS console or a single API call—without any application code changes.

Answer

Use Amazon ElastiCache for caching

Answer

Enable Multi-AZ deployment

Answer

Increase the instance size of the primary DB

Question 2

A data engineer needs to store JSON documents that are accessed by a key-value pattern. The workload requires single-digit millisecond latency at any scale. Which AWS service is most appropriate?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is a fully managed NoSQL key-value and document database that delivers single-digit millisecond latency at any scale. It is optimized for key-value access patterns, making it the ideal choice for storing and retrieving JSON documents by a primary key with consistent low latency.

Answer

Amazon DocumentDB (with MongoDB compatibility)

Answer

Amazon RDS for PostgreSQL

Answer

Amazon Neptune

Question 3

A company wants to enforce that all data in an S3 bucket is encrypted at rest using AWS KMS. Which bucket policy condition key should be used?

Accepted Answer

s3:x-amz-server-side-encryption with value aws:kms. The condition key `s3:x-amz-server-side-encryption` with value `aws:kms` enforces that objects uploaded to the S3 bucket must be encrypted using AWS KMS (SSE-KMS). This bucket policy condition ensures that any PUT request includes the `x-amz-server-side-encryption` header set to `aws:kms`, thereby enforcing encryption at rest with KMS-managed keys.

Answer

s3:x-amz-acl with value bucket-owner-full-control

Answer

s3:x-amz-server-side-encryption with value AES256

Answer

aws:SourceIp with value 10.0.0.0/8

Question 4

A data engineer is designing a disaster recovery strategy for an Amazon RDS for PostgreSQL database. The primary database is in us-east-1. Which TWO approaches provide cross-region disaster recovery?

Accepted Answer

Configure cross-region automated backups to copy to us-west-2.. Amazon RDS supports cross-region automated backups, which automatically copy backup data (snapshots and transaction logs) from the primary region (us-east-1) to a secondary region (us-west-2). This provides a fully managed, automated disaster recovery solution that allows point-in-time recovery in the secondary region without manual intervention.

Answer

Take a manual snapshot and copy it to us-west-2 daily.

Answer

Use Amazon S3 cross-region replication for the database export.

Answer

Enable Multi-AZ in us-east-1.

Question 5

A company is migrating a large Oracle data warehouse to Amazon Redshift. Which THREE considerations are important for optimizing the Redshift cluster?

Accepted Answer

Defining appropriate sort keys for the tables.. Sort keys in Amazon Redshift determine the physical order of data on disk, which directly impacts the efficiency of range-restricted queries and compression. By defining appropriate sort keys (compound or interleaved), the query optimizer can use zone maps to skip large blocks of data that don't match the filter criteria, significantly reducing the number of blocks scanned and improving query performance.

Answer

Purchasing reserved instances for the cluster.

Answer

Using columnar storage format.

Question 6

A data engineer is setting up Amazon S3 event notifications to trigger an AWS Lambda function when new objects are uploaded. Which TWO actions are required to enable this?

Accepted Answer

Add a resource-based policy to the Lambda function to allow S3 to invoke it.. Lambda functions use a resource-based policy (also known as a function policy) to grant permissions to other AWS services, such as S3, to invoke the function. Without this policy, S3 will receive an access denied error when trying to trigger the Lambda function. Option D is correct because you must configure an S3 event notification on the bucket for the `s3:ObjectCreated:*` event type to instruct S3 to send a notification to the Lambda function when new objects are uploaded.

Answer

Enable S3 versioning on the bucket.

Answer

Create an S3 bucket policy that grants S3 permission to invoke Lambda.

Answer

Set up an Amazon CloudWatch Events rule to detect S3 uploads.

Question 7

The exhibit shows an S3 bucket policy. What is the effect of this policy?

Accepted Answer

Allows only GetObject and PutObject over HTTPS.. The S3 bucket policy in the exhibit uses a condition key `aws:SecureTransport` set to `true`, which restricts access to HTTPS only. The `Effect` is `Allow` for `s3:GetObject` and `s3:PutObject` actions, meaning only these two actions are permitted over HTTPS. This matches option D.

Answer

Allows all S3 actions over HTTPS only.

Answer

Allows all S3 actions to the bucket over any protocol.

Answer

Denies all S3 actions to the bucket.

Question 8

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 9

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 10

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 11

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 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.