DEA-C01 Data Store Management Practice Test 29 — 15 Questions

Question 1

A data engineer needs to migrate an on-premises MongoDB database to AWS. The migration must have minimal downtime and support automatic scaling. Which TWO AWS services should the engineer use for the target data store? (Choose TWO.)

Accepted Answer

Amazon DocumentDB (with MongoDB compatibility). Options A and D are correct. Amazon DocumentDB is MongoDB-compatible; Amazon DynamoDB is a NoSQL database that can handle document-like data and supports auto scaling. Option B (RDS) is relational; Option C (Redshift) is for analytics; Option E (S3) is object storage, not a database.

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL

Answer

Amazon S3

Question 2

Refer to the exhibit. A data engineer is analyzing a query performance issue on an Amazon Redshift table. The table 'sales' has 100 million rows. The query is performing a full table scan. Which optimization should the engineer apply to improve query performance?

Accepted Answer

Use a compound sort key on (sale_date, region).. Option D is correct. The query filters on sale_date and aggregates by region. A compound sort key starting with sale_date enables Redshift to skip blocks that don't match the date range, reducing scan. Option A is wrong because DISTKEY product_id is fine for joins but not for this query. Option B is wrong because DISTSTYLE ALL would replicate data, increasing storage and not improving scan. Option C is wrong because interleaved sort key can be less efficient for range-restricted queries.

Answer

Change DISTKEY to region.

Answer

Use an interleaved sort key on (sale_date, region).

Answer

Change DISTSTYLE to ALL.

Question 3

A media company stores video files in an S3 bucket. The files are processed by a fleet of EC2 instances that read the files, add watermarks, and write the output back to the same bucket. Recently, the processing jobs have been failing with '500 Internal Server Error' and '503 Slow Down' errors. The data engineer checks the S3 bucket metrics and sees that the PUT/GET request rate is consistently above 5,500 requests per second for a single prefix. The engineer needs to resolve the errors with minimal changes to the application code. Which course of action should the engineer take?

Accepted Answer

Modify the application to add a random hash prefix to the object keys to distribute load across multiple prefixes.. Option A is correct. Distributing objects across multiple prefixes (e.g., by adding a hash prefix) increases the request rate limit because S3 supports up to 5,500 requests per second per prefix. Option B is wrong because S3 Transfer Acceleration improves speed over distance but does not increase request rate limits. Option C is wrong because increasing EC2 instances would increase request rate, worsening the issue. Option D is wrong because S3 Batch Operations is for large-scale batch operations, not for real-time processing.

Answer

Use S3 Batch Operations to process the files.

Answer

Increase the number of EC2 instances to process files in parallel.

Answer

Enable S3 Transfer Acceleration on the bucket to improve throughput.

Question 4

A financial services company has an Amazon DynamoDB table named 'Transactions' with provisioned read capacity of 10,000 RCU and write capacity of 5,000 WCU. The table stores transaction records for the past 90 days. The application performs point reads by transaction ID (partition key) and range queries by customer ID and timestamp (GSI). Recently, the company started a new marketing campaign, causing a sudden spike in write traffic. The write capacity is now at 4,500 WCU, and the application is experiencing occasional throttling on writes. The data engineer needs to ensure that writes are not throttled during future campaigns, while keeping costs low. The table currently has auto scaling enabled with a maximum capacity of 10,000 WCU. Which solution should the engineer implement?

Accepted Answer

Switch the table to DynamoDB on-demand capacity mode.. Option C is correct. DynamoDB on-demand mode automatically scales to accommodate traffic spikes, eliminating throttling without manual intervention. Option A is wrong because increasing max auto scaling setting still has a limit and may not react quickly enough. Option B is wrong because using SQS adds latency and complexity; not ideal for real-time. Option D is wrong because DAX is for reads, not writes.

Answer

Use DynamoDB Accelerator (DAX) to cache write requests.

Answer

Implement an Amazon SQS queue to buffer write requests and process them in batches.

Answer

Increase the maximum write capacity in the auto scaling configuration to 20,000 WCU.

Question 5

A company runs an Amazon RDS for PostgreSQL database for its e-commerce platform. The application team reports that write-intensive workloads are causing high latency and the database is experiencing storage bottlenecks. The database currently uses General Purpose SSD (gp2) storage. Which action would be MOST effective in improving write performance without changing the database instance class?

Accepted Answer

Change the storage type to General Purpose SSD (gp3).. D is correct because gp3 storage provides a baseline performance that is higher than gp2 for the same storage size, and it allows you to independently provision IOPS and throughput without needing to increase storage. This directly addresses the write-intensive workload's high latency and storage bottleneck by offering up to 4,000 IOPS at no additional cost (compared to gp2's 3,000 IOPS baseline for larger volumes), and you can scale IOPS up to 16,000 without changing the instance class.

Answer

Create a read replica and offload writes to it.

Answer

Switch the storage type to Provisioned IOPS SSD (io1).

Answer

Enable Multi-AZ deployment for high availability.

Question 6

A data engineer is designing a data lake on Amazon S3 for a healthcare organization that must comply with HIPAA regulations. The data includes protected health information (PHI) and must be encrypted at rest. The organization requires that all encryption keys be managed by AWS and rotated automatically every year. Additionally, the data must be replicated to another AWS Region for disaster recovery. Which combination of S3 features should the engineer use to meet these requirements?

Accepted Answer

Use SSE-S3 with S3 Cross-Region Replication (CRR).. Option C is correct because SSE-S3 uses AWS-managed keys that are automatically rotated, and S3 Cross-Region Replication (CRR) replicates objects to another region. Option A is incorrect because SSE-KMS uses customer-managed keys, not AWS-managed keys. Option B is incorrect because S3 Same-Region Replication does not replicate to another region. Option D is incorrect because SSE-C uses customer-provided keys, not AWS-managed.

Answer

Use SSE-S3 with S3 Same-Region Replication (SRR).

Answer

Use SSE-KMS with S3 Cross-Region Replication (CRR).

Answer

Use SSE-C with S3 Cross-Region Replication (CRR).

Question 7

A company stores its application logs in an Amazon S3 bucket. The logs are accessed frequently for the first 30 days, after which they are rarely accessed but must be retained for 7 years for compliance. The company wants to optimize storage costs while maintaining immediate retrieval availability for the first 30 days and the ability to retrieve logs within 12 hours after that. Which lifecycle policy should the data engineer configure?

Accepted Answer

Transition objects to S3 Standard-IA after 30 days and then to S3 Glacier Deep Archive after 1 year.. Option B is correct because S3 Standard-IA is for infrequently accessed data but with immediate retrieval; after 30 days, transition to S3 Glacier Deep Archive for long-term retention with retrieval within 12 hours. Option A is incorrect because S3 One Zone-IA is not durable enough for compliance. Option C is incorrect because S3 Glacier Flexible Retrieval has retrieval times of minutes to hours, not up to 12 hours; Deep Archive is cheaper. Option D is incorrect because deleting after 30 days violates retention requirement.

Answer

Delete objects after 30 days to minimize storage costs.

Answer

Transition objects to S3 One Zone-IA after 30 days and delete after 7 years.

Answer

Transition objects to S3 Glacier Flexible Retrieval after 30 days and delete after 7 years.

Question 8

A data engineering team is using Amazon DynamoDB to store user session data for a web application. The application experiences sudden spikes in traffic, causing throttling on the DynamoDB table. The team wants to minimize throttling without over-provisioning read/write capacity. Which solution should the team implement?

Accepted Answer

Enable DynamoDB Accelerator (DAX) caching layer.. Option D is correct because DynamoDB Accelerator (DAX) provides a fully managed in-memory cache that reduces read load on the table, thus minimizing throttling for read-heavy workloads. Option A is incorrect because disabling auto scaling would worsen throttling. Option B is incorrect because read replicas are for RDS, not DynamoDB. Option C is incorrect because adding a TTL does not reduce throttling; it only expires old data.

Answer

Enable DynamoDB Time to Live (TTL) to automatically delete expired items.

Answer

Disable auto scaling and manually set a high provisioned capacity.

Answer

Use Amazon RDS read replicas to offload read traffic.

Question 9

A company uses Amazon S3 to store large datasets for analytics. Each dataset is stored in a separate prefix and consists of thousands of small objects (1-10 KB each). The company notices that listing objects in a prefix takes several seconds, slowing down data processing. Which solution would MOST improve listing performance?

Accepted Answer

Use S3 Inventory to generate a daily listing of objects.. S3 Inventory provides a scheduled CSV/Parquet file listing all objects in a bucket or prefix, including metadata like size and last modified date. By querying this inventory file instead of issuing real-time ListObject API calls, you avoid the latency of enumerating thousands of small objects, dramatically improving listing performance for analytics workflows.

Answer

Add a lifecycle policy to transition objects to S3 Glacier.

Answer

Use S3 Select to filter objects during listing.

Answer

Increase the number of parallel requests by using more prefixes.

Question 10

A company is migrating an on-premises MySQL database to Amazon RDS for MySQL. The database is 500 GB in size. The migration must have minimal downtime and must be completed within a week. Which AWS service should the data engineer use to perform the migration?

Accepted Answer

AWS Database Migration Service (DMS).. Option A is correct because AWS Database Migration Service (DMS) supports minimal downtime migration with ongoing replication from on-premises to RDS. Option B is incorrect because S3 is object storage, not for database migration. Option C is incorrect because Snowball is for large data transfer but involves shipping and is not suitable for minimal downtime. Option D is incorrect because DataSync is for file storage, not databases.

Answer

Amazon S3 Transfer Acceleration.

Answer

AWS Snowball Edge.

Answer

AWS DataSync.

Question 11

A data engineer needs to store clickstream data from a web application in Amazon S3. Each event is about 5 KB, and the application generates 1 million events per hour. The data is used for real-time analytics and also for batch processing. The engineer wants to minimize storage costs while ensuring that data is available for real-time queries as soon as it is written. Which storage class should the engineer use for the S3 bucket?

Accepted Answer

S3 Standard.. Option C is correct because S3 Standard offers low latency and high throughput for frequently accessed data, and it is suitable for real-time analytics. Option A is incorrect because S3 Intelligent-Tiering has a monitoring cost and is optimal for unknown access patterns, but for a known frequent access pattern, Standard is cheaper. Option B is incorrect because S3 Standard-IA has a retrieval fee and is not ideal for frequent access. Option D is incorrect because S3 Glacier Instant Retrieval is for long-lived, rarely accessed data requiring millisecond retrieval, but it has a higher cost per GB than Standard for frequent access.

Answer

S3 Intelligent-Tiering.

Answer

S3 Standard-IA.

Answer

S3 Glacier Instant Retrieval.

Question 12

A company uses Amazon DynamoDB to store metadata for a document management system. The table has a partition key of document_id and a sort key of version. The application frequently queries for the latest version of a document by document_id. The data engineer notices that these queries are consuming a lot of read capacity. How can the engineer optimize the read performance and reduce read capacity consumption?

Accepted Answer

Create a global secondary index (GSI) and use DynamoDB Accelerator (DAX).. Option B is correct because creating a global secondary index (GSI) with document_id as partition key and version as sort key, but with a different projection, can allow queries to use the index with fewer items returned. More importantly, using DynamoDB Accelerator (DAX) would cache the results of frequent queries, reducing read capacity consumption. Option A is incorrect because changing the sort key order does not reduce read capacity for the same query. Option C is incorrect because read replicas are not a feature of DynamoDB. Option D is incorrect because decreasing ReadCapacityUnits would cause throttling.

Answer

Change the sort key to store version in descending order.

Answer

Enable DynamoDB Streams and use a read replica.

Answer

Decrease the ReadCapacityUnits of the table to force caching.

Question 13

A data engineer is designing a data lake on Amazon S3 that will store sensitive financial data. The engineer needs to implement encryption at rest and ensure that only authorized users can access the data. Which TWO actions should the engineer take to meet these requirements? (Choose TWO.)

Accepted Answer

Configure a bucket policy that denies writes if the object is not encrypted.. Option A is correct because S3 bucket policies can be used to enforce encryption and control access. Option C is correct because IAM policies define user permissions. Option B is incorrect because SSE-C is not recommended as it requires managing your own keys. Option D is incorrect because S3 Transfer Acceleration is for speed, not security. Option E is incorrect because ACLs are legacy and not recommended for access control.

Answer

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

Answer

Enable S3 Transfer Acceleration for the bucket.

Answer

Enable object-level access control lists (ACLs).

Question 14

A company runs a production Amazon RDS for PostgreSQL database. The database is experiencing performance degradation due to a high number of concurrent read queries. The data engineer needs to improve read performance without significantly increasing costs. Which TWO actions should the engineer take? (Choose TWO.)

Accepted Answer

Create one or more read replicas in the same region.. Option A is correct because read replicas offload read traffic from the primary instance. Option D is correct because performance insights help identify bottlenecks. Option B is incorrect because Multi-AZ does not improve read performance. Option C is incorrect because increasing storage size may not help with read performance. Option E is incorrect because deleting indexes would degrade performance.

Answer

Enable Multi-AZ deployment for automatic failover.

Answer

Increase the allocated storage size to improve IOPS.

Answer

Delete unnecessary indexes to reduce write overhead.

Question 15

A data engineer is using Amazon DynamoDB to store session data for a web application. The engineer wants to ensure that all data is encrypted at rest using an AWS managed key. Which THREE steps should the engineer take to achieve this? (Choose THREE.)

Accepted Answer

Specify an AWS KMS customer managed key for encryption if required.. Option C is correct because when using DynamoDB encryption at rest, you can choose between an AWS managed key (aws/dynamodb) or a customer managed key (CMK) in AWS KMS. Specifying a customer managed key is a valid step if the requirement is to use an AWS managed key, but the question asks for steps to achieve encryption with an AWS managed key, so selecting a customer managed key would be incorrect unless the engineer intends to use it; however, the option states 'if required', which aligns with the flexibility to choose. Option E is correct because creating the DynamoDB table with encryption at rest enabled using an AWS managed key directly fulfills the requirement—DynamoDB defaults to the AWS managed key when encryption is enabled without specifying a CMK.

Answer

Enable server-side encryption with S3-managed keys (SSE-S3) on the DynamoDB table.

Answer

Disable encryption at rest to improve performance.

Answer

Use client-side encryption before writing data to DynamoDB.