DEA-C01 Data Store Management Practice Test 3 — 15 Questions

Question 1

A data engineer runs the AWS CLI command shown in the exhibit to list objects in an S3 bucket. The command returns only two objects even though the bucket contains thousands of objects under the prefix. What should the engineer do to retrieve the next batch of objects?

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

Accepted Answer

Use the --starting-token parameter with the value from the NextToken field.. The AWS CLI `list-objects-v2` command paginates results by default. When the output is truncated, the response includes a `NextToken` field. To retrieve the next batch, the engineer must use the `--starting-token` parameter with the value from that `NextToken` field, which tells the CLI to resume listing from where it left off.

Answer

Increase the --max-items value to a larger number.

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Use the --page-size parameter to request more items per API call.

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Change the --prefix to a more specific value.

Question 2

A data engineer deploys the CloudFormation template shown in the exhibit. After 60 days, what will be the storage class of objects in the bucket?

Accepted Answer

The objects will be in GLACIER storage class.. The CloudFormation template includes a lifecycle rule with a transition action to the GLACIER storage class after 60 days from object creation. Since the rule is properly configured and no expiration action is defined, objects will be moved from STANDARD to GLACIER at day 60. This is standard S3 lifecycle behavior, and objects are not deleted unless a separate expiration rule is set.

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The objects will be deleted.

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The objects will remain in STANDARD storage class because the rule is not triggered.

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The objects will be immediately transitioned to GLACIER upon creation.

Question 3

A company is using Amazon RDS for PostgreSQL and wants to minimize downtime during a major version upgrade. Which approach best meets this requirement?

Accepted Answer

Create a read replica of the current instance, upgrade the replica, and then promote it to primary.. Creating a read replica, upgrading it to the new major version, and then promoting it to primary minimizes downtime by allowing the replica to be upgraded while the original instance remains operational. The promotion process is fast, typically taking only a few seconds to redirect traffic, and avoids the longer downtime associated with in-place upgrades or full data migrations.

Answer

Perform an in-place upgrade using the AWS Management Console.

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Modify the DB instance class to a larger size to handle the upgrade.

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Use pg_dump and pg_restore to migrate data to a new upgraded instance.

Question 4

A data engineer needs to store semi-structured JSON logs from an application for up to 30 days, with infrequent access. Which storage solution is the most cost-effective?

Accepted Answer

Amazon S3 Standard-Infrequent Access (S3 Standard-IA). Amazon S3 Standard-Infrequent Access (S3 Standard-IA) is the most cost-effective choice for storing semi-structured JSON logs for up to 30 days with infrequent access. It offers low storage cost (compared to S3 Standard) while providing low-latency retrieval and high durability (99.999999999%) across multiple Availability Zones, making it ideal for data that is accessed less frequently but needs immediate availability when requested.

Answer

Amazon S3 Glacier Deep Archive

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Amazon S3 One Zone-Infrequent Access (S3 One Zone-IA)

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Amazon S3 Standard

Question 5

A data engineer is troubleshooting an Amazon RDS for MySQL instance that is experiencing high read latency. The instance is a Single-AZ db.r5.large with 100 GB of General Purpose (gp2) storage. Which action is most likely to reduce read latency?

Accepted Answer

Create a read replica and direct read queries to it.. Creating a read replica offloads SELECT queries from the primary instance, directly reducing the read load and thus read latency. Since the instance is Single-AZ and experiencing high read latency, a read replica distributes the read traffic without altering the existing storage or availability configuration.

Answer

Enable automatic backups with a 7-day retention.

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Increase the allocated storage to 200 GB.

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Convert the instance to a Multi-AZ deployment.

Question 6

A company is building a real-time analytics dashboard using Amazon Kinesis Data Streams and Amazon DynamoDB. The data engineer needs to ensure that the DynamoDB table can handle write spikes without throttling. Which approach is the most cost-effective?

Accepted Answer

Use DynamoDB on-demand capacity mode.. DynamoDB on-demand capacity mode automatically scales to handle write spikes without requiring capacity planning or management, making it the most cost-effective choice for unpredictable workloads like a real-time analytics dashboard. It charges per request, so you only pay for the writes you actually use, avoiding over-provisioning costs.

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Use DynamoDB Accelerator (DAX) to cache writes.

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Use provisioned capacity with auto-scaling set to a maximum of 10,000 WCU.

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Use an Amazon Lambda function to buffer writes and batch them to DynamoDB.

Question 7

Which THREE factors should a data engineer consider when choosing between Amazon Redshift and Amazon Athena for querying large datasets in Amazon S3? (Choose three.)

Accepted Answer

Redshift requires provisioning and managing clusters, while Athena is serverless.. Option B is correct because Redshift is a provisioned, cluster-based data warehouse where you choose node types and manage (or use RA3/Serverless variants of) compute, whereas Athena is fully serverless and requires no infrastructure management, which is a key architectural decision factor. Option C is correct because the cost models differ fundamentally: Athena bills per query based on the amount of data scanned (with a 10 MB minimum per query), while Redshift bills for the cluster's compute capacity (per node-hour) regardless of query volume, so cost predictability and workload patterns matter. Option E is correct because Redshift is optimized for highly structured, frequently queried data with distribution and sort keys, columnar storage, and result caching, while Athena is well suited for ad-hoc, exploratory queries directly against raw or semi-structured data in S3 using the Glue Data Catalog. Option A is not a differentiating factor for the decision since both engines support standard SQL, so it does not help choose between them. Option D is inaccurate because Redshift can query data in S3 via Redshift Spectrum and COPY, and Athena is not limited to S3 in the sense that it queries data in S3 through cataloged sources, so the statement mischaracterizes the trade-off.

Answer

Both support standard SQL queries.

Answer

Athena can only query data stored in Amazon S3, while Redshift can also query data in S3.

Question 8

Which TWO features of Amazon DynamoDB help ensure high availability and durability? (Choose two.)

Accepted Answer

Data is automatically replicated across multiple Availability Zones within an AWS Region.. DynamoDB automatically replicates data synchronously across three Availability Zones (AZs) within an AWS Region. This built-in replication ensures that even if an entire AZ fails, the data remains available and durable, providing a 99.999999999% (11 nines) durability SLA.

Answer

Auto-scaling adjusts provisioned capacity based on traffic.

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Global tables enable active-active replication across multiple AWS Regions.

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Time to Live (TTL) automatically deletes expired items.

Question 9

A company stores sensitive user data in an Amazon RDS for PostgreSQL DB instance. A security audit requires that all data be encrypted at rest. The database is currently unencrypted. What is the MOST operationally efficient way to enable encryption at rest?

Accepted Answer

Take a snapshot of the DB instance, copy it with encryption enabled, and restore the snapshot to a new DB instance.. RDS for PostgreSQL does not support enabling encryption at rest on an existing unencrypted DB instance directly. The only way to achieve this is by taking a snapshot of the unencrypted instance, creating an encrypted copy of that snapshot, and then restoring it to a new encrypted DB instance. This method is operationally efficient as it uses native RDS snapshot copy and restore capabilities without requiring additional infrastructure or manual data migration.

Answer

Create a read replica with encryption enabled and promote it.

Answer

Modify the DB instance and enable encryption in the console.

Answer

Modify the DB parameter group to include encryption parameters and reboot the instance.

Question 10

A data engineer is designing a data lake on Amazon S3 for storing raw sensor data. The data is append-only and accessed infrequently after 30 days. Compliance requires that data be retained for 7 years. Which S3 storage class is the MOST cost-effective for data older than 30 days?

Accepted Answer

S3 Glacier Deep Archive. B is correct because Amazon S3 Glacier Deep Archive is the most cost-effective storage class for data that is accessed infrequently and must be retained for long periods (7 years). For data older than 30 days, the retrieval time of 12 hours is acceptable given the append-only, infrequent access pattern, and the storage cost is significantly lower than other classes.

Answer

S3 Standard-IA

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S3 One Zone-IA

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S3 Intelligent-Tiering

Question 11

A company uses Amazon EMR to process large datasets stored in Amazon S3. The cluster uses a transient configuration and stores intermediate data on HDFS. After a job fails due to a spot instance termination, the data engineer needs to rerun the job. What should the engineer do to minimize data loss and cost?

Accepted Answer

Configure the cluster with a mix of spot and on-demand instances and set HDFS replication to 3.. Using a mix of spot and on-demand instances balances cost savings with fault tolerance, while setting HDFS replication to 3 ensures that intermediate data on HDFS survives the loss of a single node (e.g., a terminated spot instance). This allows the job to resume from the last checkpoint or reduce recomputation, minimizing both data loss and cost.

Answer

Use a long-running cluster with all on-demand instances to avoid interruptions.

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Configure the cluster to use EMRFS and store intermediate data in S3.

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Increase the HDFS replication factor to 5 and use only spot instances.

Question 12

A data engineer is migrating an on-premises Apache Cassandra cluster to Amazon Keyspaces (for Apache Cassandra). The cluster has 10 TB of data. The migration must minimize application downtime. Which strategy should the engineer use?

Accepted Answer

Set up a dual-write pattern where the application writes to both the on-premises cluster and Keyspaces, then switch reads to Keyspaces once data is synchronized.. The dual-write pattern allows the application to write to both the on-premises Cassandra cluster and Amazon Keyspaces simultaneously, ensuring data consistency with minimal downtime. Once the existing data is backfilled and the systems are synchronized, reads can be switched to Keyspaces with near-zero application interruption. This approach avoids the downtime required for bulk export/import or snapshot restore.

Answer

Export the data using the Cassandra COPY command and import it into Keyspaces using the COPY command.

Answer

Take a snapshot of the on-premises cluster and restore it to Keyspaces using the Keyspaces console.

Answer

Use AWS Database Migration Service (DMS) to continuously replicate data from the on-premises cluster to Keyspaces.

Question 13

A company uses Amazon DynamoDB to store session data for a web application. The application experiences sudden spikes in traffic, causing occasional throttling errors. The data engineer needs to handle these spikes without over-provisioning capacity. What is the MOST cost-effective solution?

Accepted Answer

Configure DynamoDB Auto Scaling to automatically adjust provisioned capacity.. DynamoDB Auto Scaling (option C) is the most cost-effective solution because it automatically adjusts the provisioned read/write capacity based on actual traffic patterns, handling sudden spikes without manual intervention or over-provisioning. This avoids paying for unused capacity during low-traffic periods while still accommodating bursts within the configured limits.

Answer

Set up a TTL (Time to Live) attribute to automatically delete old session data.

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Enable DynamoDB Accelerator (DAX) to cache read requests.

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Switch to DynamoDB on-demand mode.

Question 14

A data engineer is designing a data warehouse using Amazon Redshift. The workload includes complex queries that join large tables. The engineer notices that queries are slow due to disk-based operations. Which configuration change would MOST improve query performance?

Accepted Answer

Choose an appropriate distribution style (e.g., KEY or ALL) for the tables.. Choosing an appropriate distribution style (KEY or ALL) minimizes data movement between nodes during query execution. In Amazon Redshift, disk-based operations often result from large volumes of data being redistributed across the network for joins. By colocating related data on the same slices via KEY distribution or replicating small tables with ALL distribution, you reduce the need for broadcast or redistribution, which directly alleviates disk-based spills and improves query performance.

Answer

Define appropriate sort keys on the large tables.

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Increase the number of slices per node by choosing a different node type.

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Enable compression on all columns.

Question 15

A company uses Amazon S3 to store historical financial records. A compliance policy requires that all objects be encrypted with a customer-managed key stored in AWS KMS. The bucket is already configured with SSE-S3. What is the LEAST disruptive way to change the encryption to SSE-KMS?

Accepted Answer

Copy all objects to a new bucket that has default encryption set to SSE-KMS.. Changing the default encryption settings of an existing bucket (SSE-S3 to SSE-KMS) does not retroactively encrypt objects that were already stored with SSE-S3. Copying all objects to a new bucket that has default encryption set to SSE-KMS ensures every object is encrypted with a customer-managed key, as the copy operation re-encrypts each object using the new bucket's default settings. This approach is the least disruptive because it avoids modifying the original bucket's configuration or policies, which could break existing applications or access patterns.

Answer

Add a bucket policy to enforce SSE-KMS.

Answer

Update the bucket's default encryption settings to SSE-KMS.

Answer

Use S3 Batch Operations to apply SSE-KMS to all existing objects.