DEA-C01 Data Store Management Practice Test 11 — 15 Questions

Question 1

A data engineer is designing a data lake on Amazon S3. The data is accessed frequently for the first 30 days, then rarely after that. Compliance requires that data be retained for 7 years. What is the MOST cost-effective storage strategy?

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

Accepted Answer

Use S3 Standard for 30 days, then transition to S3 Standard-IA, then to S3 Glacier Deep Archive after 90 days.. The most cost-effective because it matches the access pattern: S3 Standard for the first 30 days of frequent access, then S3 Standard-IA for the next 60 days (reduced storage cost with a retrieval fee), and finally S3 Glacier Deep Archive for the remaining ~6.9 years to meet the 7-year retention requirement at the lowest possible storage cost. This lifecycle policy minimizes total cost by transitioning data to progressively cheaper storage tiers as access frequency drops, while still meeting compliance.

Answer

Use S3 Intelligent-Tiering for the entire 7 years.

Answer

Store all data in S3 Standard for 7 years.

Answer

Use S3 Standard for 30 days, then S3 One Zone-IA for 7 years.

Question 2

A company runs an Amazon RDS for PostgreSQL database. To meet disaster recovery requirements, they set up a cross-Region read replica. The replica has been lagging by several minutes. Which action is MOST effective to reduce the replica lag?

Accepted Answer

Increase the instance size (memory and CPU) of the replica.. Increasing the instance size (memory and CPU) of the cross-Region read replica is the most effective action because replica lag in Amazon RDS for PostgreSQL is often caused by the replica being unable to keep up with the volume of write-ahead log (WAL) data arriving from the primary. A larger replica instance provides more compute and memory resources to apply WAL changes faster, reducing the replay lag. This directly addresses the bottleneck at the replica side without impacting the primary database.

Answer

Enable Multi-AZ on the primary database.

Answer

Increase the instance size of the primary database.

Answer

Decrease the instance size of the replica to reduce cost.

Question 3

A company is using Amazon DynamoDB for a gaming application. They want to store player session data that expires after 24 hours. Which DynamoDB feature should be used?

Accepted Answer

Time to Live (TTL). Amazon DynamoDB Time to Live (TTL) allows you to define a per-item timestamp attribute that automatically deletes items after a specified duration. For the gaming session data that must expire after 24 hours, you can set the TTL attribute to the current time plus 24 hours, and DynamoDB will asynchronously delete expired items without any additional cost or write operations.

Answer

DynamoDB Streams

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Global Tables

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Point-in-Time Recovery

Question 4

A data engineer is migrating an on-premises Apache HBase workload to Amazon DynamoDB. The application requires strongly consistent reads and the ability to query by a composite key (partition key + sort key). Which DynamoDB table design should be used?

Accepted Answer

Create a table with a partition key and sort key, and use ConsistentRead parameter.. DynamoDB natively supports strongly consistent reads when you use the `ConsistentRead` parameter set to `true` on GetItem, Query, or Scan operations. By defining a table with a partition key and sort key, you can directly query by the composite key (partition key + sort key) with strong consistency, meeting both requirements without additional infrastructure.

Answer

Use a secondary index with strongly consistent reads.

Answer

Use a local secondary index (LSI) with the composite key.

Answer

Create a global secondary index (GSI) with the composite key.

Question 5

A company has an Amazon Redshift cluster that stores petabytes of data. Queries are experiencing high disk usage due to large intermediate results. The data engineer needs to improve query performance without adding more nodes. Which action should the engineer take?

Accepted Answer

Set appropriate distribution keys to minimize data movement.. Setting appropriate distribution keys can minimize data movement during joins and aggregations, which directly reduces the size of intermediate results spilled to disk. This improves query performance without adding nodes. Option C (compression) reduces storage size and I/O but does not directly address disk usage from large intermediate results. Option B (WLM) limits concurrency, not disk usage. Option D (sort keys) improves scan efficiency, not intermediate result size.

Answer

Configure workload management (WLM) queues to limit concurrency.

Answer

Apply column compression encoding to reduce data size.

Answer

Define sort keys on all columns used in WHERE clauses.

Question 6

A company is using Amazon S3 to store sensitive data. They need to ensure that all objects are encrypted at rest. Which combination of actions should be taken? (Choose TWO.)

Accepted Answer

Use a bucket policy to deny PutObject requests that do not include the x-amz-server-side-encryption header.. A bucket policy that denies PutObject requests lacking the `x-amz-server-side-encryption` header enforces encryption at the time of upload, ensuring that any object written without explicit encryption headers is rejected. Option E is correct because enabling default encryption on the S3 bucket automatically applies server-side encryption (SSE-S3 or SSE-KMS) to any object uploaded without specifying encryption headers, providing a fallback that covers all objects. Together, these actions ensure that every object stored in the bucket is encrypted at rest, either by explicit client request or by default bucket settings.

Answer

Enable S3 Versioning on the bucket.

Answer

Enable MFA Delete on the bucket.

Answer

Configure S3 Access Points with network policies.

Question 7

A company uses Amazon Redshift for analytics. They notice that some queries are slow due to data redistribution. The data engineer wants to minimize data movement across nodes. Which table design strategy should be used? (Choose TWO.)

Accepted Answer

Choose a distribution key that matches the join key for large tables.. When large tables are joined on their distribution keys, Redshift can perform a collocated join, meaning the matching rows are already on the same node slice, eliminating the need to redistribute data across the network. This directly minimizes data movement and speeds up query execution.

Answer

Set the distribution style to AUTO for all tables.

Answer

Define compound sort keys on frequently filtered columns.

Answer

Use EVEN distribution for all tables.

Question 8

A company is using Amazon S3 for data lake storage. They need to query the data directly using SQL without loading it into a database. Which AWS service should be used?

Accepted Answer

Amazon Athena. Amazon Athena is the correct choice because it is a serverless, interactive query service that allows you to analyze data directly in Amazon S3 using standard SQL, without needing to load or transform the data into a database. Athena uses Presto under the hood and supports querying structured, semi-structured, and unstructured data formats (e.g., CSV, JSON, Parquet, ORC) stored in S3, making it ideal for ad-hoc SQL queries on a data lake.

Answer

Amazon Redshift Spectrum

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Amazon EMR

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AWS Glue

Question 9

A company is using Amazon DynamoDB for an e-commerce application. The application experiences sudden spikes in traffic, causing throttling errors. The data engineer needs to handle the spikes cost-effectively. Which solution should be used?

Accepted Answer

Use DynamoDB auto scaling with a target utilization of 70%.. DynamoDB auto scaling with a target utilization of 70% allows the table to dynamically adjust provisioned read/write capacity based on actual traffic patterns, handling sudden spikes without manual intervention while avoiding over-provisioning. This balances performance and cost by scaling up during spikes and scaling down during low traffic, preventing throttling errors cost-effectively.

Answer

Implement DynamoDB Accelerator (DAX) to cache reads.

Answer

Switch to DynamoDB on-demand capacity mode.

Answer

Provision high read and write capacity units to handle peak traffic.

Question 10

A data engineer reviews this IAM policy attached to an S3 bucket. What is the effect of this policy?

Accepted Answer

Allows PutObject only when the object is encrypted with SSE-KMS.. The IAM policy uses a Deny effect with a StringNotEquals condition on s3:x-amz-server-side-encryption for aws:kms. This means that if the encryption header is anything other than aws:kms (i.e., not SSE-KMS), the request is denied. The net effect is that PutObject is allowed only when the object IS encrypted with SSE-KMS.

Answer

Denies PutObject when encryption is not SSE-KMS.

Answer

Denies all PutObject requests.

Answer

Allows PutObject only when the object is NOT encrypted with SSE-KMS.

Question 11

A data engineer runs this CLI command. Which query is MOST efficient against this table?

Accepted Answer

Query the CustomerIndex GSI by CustomerID and OrderDate.. The CLI command likely created a global secondary index (GSI) named CustomerIndex on CustomerID and OrderDate. Querying this GSI directly is the most efficient because it uses the index's sort key to retrieve only the relevant items without scanning the entire table, minimizing read capacity consumption.

Answer

Scan the table to find all orders for a CustomerID.

Answer

Create a local secondary index on CustomerID.

Answer

Query by OrderID and filter by OrderDate.

Question 12

A data engineer sees this AWS Glue table definition in the Data Catalog. The engineer wants to query this table with Amazon Athena, but the query returns zero rows. What is the MOST likely cause?

Accepted Answer

The data files are not in the specified S3 location.. The most likely cause is that the data files are not in the specified S3 location. When an AWS Glue table is defined in the Data Catalog, Athena reads the table's metadata (including the S3 location) and then attempts to read the underlying data files from that exact path. If the files are missing, misnamed, or in a different prefix, Athena returns zero rows because there is no data to scan. This is a common misconfiguration when the S3 path in the table definition does not match the actual data storage.

Answer

The SerDe library is incorrect for CSV files.

Answer

The table format CSV is not supported by Athena.

Answer

Athena cannot read tables from the Glue Data Catalog.

Question 13

A CloudFormation template includes this IAM policy for a cross-account S3 upload use case. What is the purpose of the condition?

Accepted Answer

To ensure that uploaded objects grant full control to the bucket owner.. The condition in the IAM policy uses the `s3:x-amz-acl` key with a value of `bucket-owner-full-control`. This ensures that any object uploaded to the S3 bucket explicitly grants the bucket owner full control over the object, overriding the default behavior where the uploading account retains ownership. This is critical in cross-account uploads to prevent the uploading account from retaining exclusive access to the objects.

Answer

To enforce server-side encryption with KMS.

Answer

To limit the size of objects that can be uploaded.

Answer

To restrict uploads to only a specific AWS account.

Question 14

A company is using Amazon RDS for MySQL and needs to automate backups with a retention period of 35 days. They also want to be able to restore to any point within the retention period. Which configuration should be used?

Accepted Answer

Set the backup retention period to 35 days and enable automatic backups.. Amazon RDS for MySQL supports automated backups with a configurable retention period of up to 35 days. By setting the backup retention period to 35 days and enabling automatic backups, RDS automatically performs daily snapshots and transaction log backups, enabling point-in-time recovery (PITR) to any second within the retention window. This meets the requirement for both a 35-day retention and full PITR capability without manual intervention.

Answer

Enable manual snapshots daily and retain for 35 days.

Answer

Set the backup retention period to 7 days and create daily manual snapshots.

Answer

Disable automated backups and rely on Multi-AZ for recovery.

Question 15

A company is storing sensitive user data in an Amazon S3 bucket. The security team requires that all data be encrypted at rest using a customer-managed key stored in AWS KMS. The bucket policy must deny any PUT request that does not include the appropriate encryption header. Which bucket policy condition key should be used?

Accepted Answer

s3:x-amz-server-side-encryption-aws-kms-key-id. The `s3:x-amz-server-side-encryption-aws-kms-key-id` condition key allows the bucket policy to enforce that PUT requests include a specific customer-managed KMS key ID in the `x-amz-server-side-encryption-aws-kms-key-id` header, ensuring encryption at rest with the required key. This directly meets the security team's requirement to deny PUT requests that lack the appropriate encryption header tied to a customer-managed KMS key.

Answer

s3:x-amz-server-side-encryption

Answer

s3:x-amz-acl

Answer

aws:SourceArn