DEA-C01 Data Store Management Practice Test 8 — 15 Questions

Question 1

A company is migrating an on-premises Apache Hadoop cluster to Amazon EMR. The cluster uses HDFS for storage. Which THREE features of Amazon EMR help reduce storage costs compared to on-premises HDFS? (Choose THREE)

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

Accepted Answer

Leverage Amazon S3 storage classes like S3 Standard-IA for older data.. Amazon S3 Standard-IA (Infrequent Access) offers lower storage costs than S3 Standard for data that is accessed less frequently, making it ideal for older or archival data in a Hadoop migration. By using S3 as the primary storage layer via EMRFS, you decouple compute from storage and avoid the replication overhead of HDFS (which typically uses 3x replication), significantly reducing storage costs.

Answer

Use instance store volumes for intermediate data.

Answer

Attach Amazon EBS volumes to cluster nodes for persistent storage.

Question 2

A data engineer is evaluating storage options for a new application that requires low-latency access to unstructured blobs (up to 5 TB each) with high throughput. The data will be accessed frequently for the first 30 days and then rarely. Which TWO storage solutions meet these requirements? (Choose TWO)

Accepted Answer

Amazon S3 with lifecycle policies. Amazon S3 with lifecycle policies is correct because S3 provides low-latency access to unstructured blobs (up to 5 TB each) with high throughput, and lifecycle policies can automatically transition objects to colder storage tiers (e.g., S3 Glacier Deep Archive) after 30 days, matching the access pattern of frequent then rare access.

Answer

Amazon EBS with io2 Block Express volumes

Answer

Amazon EFS

Answer

Amazon RDS for PostgreSQL

Question 3

A company is using an RDS for PostgreSQL instance and wants to minimize downtime during a major version upgrade. Which approach should be taken?

Accepted Answer

Create a read replica of the DB instance, upgrade the replica, and then promote it to the primary instance.. Creating a read replica of the RDS for PostgreSQL instance, upgrading the replica to the new major version, and then promoting it to become the primary instance minimizes downtime by allowing the replica to be upgraded while the original primary remains fully operational. The promotion process is fast (typically seconds), and the only downtime is the brief cutover period when applications switch to the promoted replica. This approach leverages RDS's managed replication and avoids the longer downtime associated with direct in-place upgrades.

Answer

Use AWS Database Migration Service (DMS) to migrate data to a new upgraded instance.

Answer

Modify the DB instance and apply the upgrade immediately.

Answer

Take a snapshot of the DB instance and restore it as a new instance with the upgraded version.

Question 4

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. The engineer needs to minimize storage costs while ensuring data is available within minutes for the first 30 days and can be retrieved within 12 hours after that. Which lifecycle policy should be applied?

Accepted Answer

Transition to S3 Glacier Deep Archive after 30 days.. S3 Glacier Deep Archive offers the lowest storage cost for data that is rarely accessed after 30 days, and its retrieval time (within 12 hours) matches the requirement. The lifecycle policy transitions objects from S3 Standard (or S3 Intelligent-Tiering) to S3 Glacier Deep Archive after 30 days, minimizing costs while meeting the 12-hour retrieval window.

Answer

Transition to S3 One Zone-IA after 30 days.

Answer

Transition to S3 Standard-IA after 30 days.

Answer

Transition to S3 Glacier Flexible Retrieval after 30 days.

Question 5

A company uses DynamoDB with provisioned capacity and experiences throttling on a table during peak hours. The data engineer notices that the table has a partition key with high cardinality and the workload is read-heavy. Which action would best resolve the throttling?

Accepted Answer

Enable DynamoDB Auto Scaling for the table.. DynamoDB Auto Scaling adjusts the provisioned read capacity units (RCUs) based on actual traffic patterns, preventing throttling during peak hours without manual intervention. Since the table has high-cardinality partition keys and is read-heavy, throttling is likely due to insufficient RCUs, which Auto Scaling dynamically increases to match demand.

Answer

Switch the table to on-demand capacity mode.

Answer

Increase the provisioned write capacity units.

Answer

Add a global secondary index (GSI) to distribute reads.

Question 6

A data engineer needs to store semi-structured JSON logs from multiple sources in a centralized data store for querying using SQL. The logs are immutable and need to be retained for 90 days. Which AWS service should be used?

Accepted Answer

Amazon S3 with Amazon Athena.. Amazon S3 with Amazon Athena is the correct choice because S3 provides durable, cost-effective storage for immutable semi-structured JSON logs, and Athena enables serverless SQL querying directly against the data in S3 without needing to load or transform it. This combination meets the 90-day retention requirement and supports querying semi-structured data using standard SQL via Athena's built-in JSON SerDe.

Answer

Amazon RDS for MySQL.

Answer

Amazon DynamoDB.

Answer

Amazon ElastiCache for Redis.

Question 7

A company uses Amazon Redshift for analytics. The data engineer notices that queries are slow due to many small inserts. Which technique would improve write performance?

Accepted Answer

Use the COPY command to load data from Amazon S3.. The COPY command is the recommended way to load data into Amazon Redshift because it performs bulk inserts in parallel across all nodes, leveraging the cluster's distributed architecture. Small individual INSERT statements cause high overhead due to transaction logging and commit processing, leading to slow write performance. By loading data from Amazon S3 using COPY, you bypass these per-row overheads and achieve optimal throughput.

Answer

Define DISTKEY and SORTKEY on the table.

Answer

Increase the number of nodes in the cluster.

Answer

Configure workload management (WLM) queues.

Question 8

A data engineer is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database is 5 TB in size and has a 1 Gbps network connection. The migration must be completed within 48 hours. Which service should be used?

Accepted Answer

AWS Database Migration Service (DMS).. AWS DMS is the correct choice because it is designed for migrating databases to AWS with minimal downtime, and it can handle a 5 TB Oracle database over a 1 Gbps network within 48 hours. DMS supports ongoing replication to keep the source and target in sync, and it can use Oracle-specific features like supplemental logging and change data capture (CDC) to reduce migration time. The 1 Gbps connection provides sufficient bandwidth to transfer 5 TB in under 12 hours at full utilization, leaving ample time for setup and validation.

Answer

AWS DataSync.

Answer

Amazon S3 Transfer Acceleration.

Answer

AWS Snowball Edge.

Question 9

A company uses Amazon S3 to store sensitive data. The security team requires that all data be encrypted at rest using a customer-managed key that is rotated annually. Which encryption option should be used?

Accepted Answer

SSE-KMS (Server-Side Encryption with AWS KMS).. SSE-KMS is the correct choice because it allows you to use a customer-managed key (CMK) in AWS KMS, which you can configure to rotate automatically on an annual schedule. This satisfies the security team's requirement for encryption at rest with a key you control and rotate yearly, while still leveraging server-side encryption that integrates with S3's existing infrastructure.

Answer

SSE-S3 (Server-Side Encryption with S3-managed keys).

Answer

Client-side encryption.

Answer

SSE-C (Server-Side Encryption with Customer-Provided keys).

Question 10

A data engineer is troubleshooting a slow-running query on Amazon Redshift. The query scans a large table but returns few rows. Which diagnostic step should be taken first?

Accepted Answer

Use EXPLAIN to review the query plan.. When a query scans a large table but returns few rows, the most likely cause is an inefficient query plan—such as a full table scan instead of using indexes or zone maps. Using EXPLAIN first reveals the execution plan, allowing the engineer to identify whether the query is performing unnecessary sequential scans, missing filter pushdown, or using suboptimal join strategies. This diagnostic step should always precede tuning actions like ANALYZE or VACUUM, which address data distribution or storage bloat rather than query planning.

Answer

Run ANALYZE on the table.

Answer

Check the concurrency scaling status.

Answer

Run VACUUM on the table.

Question 11

A company uses DynamoDB with global tables in two AWS Regions. The data engineer observes that a write to the table in us-east-1 is not immediately visible in a read from eu-west-1. What is the most likely reason?

Accepted Answer

Replication between regions is eventually consistent.. DynamoDB global tables use asynchronous replication between regions. When a write occurs in us-east-1, the change is propagated to eu-west-1 with a replication lag that is typically sub-second but not instantaneous. Reads in eu-west-1 are eventually consistent by default, meaning they may not reflect the most recent write until replication completes. This is the expected behavior of DynamoDB global tables, which prioritize availability and partition tolerance over immediate consistency across regions.

Answer

The read is using strongly consistent reads.

Answer

There is a write conflict that needs to be resolved.

Answer

DynamoDB Streams is not enabled on the table.

Question 12

A data engineer needs to store event data from IoT devices that arrives in bursts. The data is key-value and requires single-digit millisecond read and write latency. The engineer also needs to run complex analytical queries on the data for reporting. Which TWO services should be used together? (Choose TWO.)

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is correct because it provides single-digit millisecond read and write latency at any scale, making it ideal for IoT event data arriving in bursts. Its key-value data model matches the requirement, and it can serve as the operational data store for fast ingestion while supporting complex analytical queries when integrated with Amazon Redshift.

Answer

Amazon ElastiCache for Redis

Answer

Amazon S3

Answer

Amazon RDS for MySQL

Question 13

A company is using Amazon S3 for a data lake. The data engineer needs to ensure that all new objects are automatically encrypted with a customer-managed KMS key and that the bucket policy enforces encryption. Which THREE steps should be taken? (Choose THREE.)

Accepted Answer

Configure default encryption on the bucket to use SSE-KMS.. Configuring default encryption on the S3 bucket to use SSE-KMS ensures that any object uploaded without an explicit encryption header is automatically encrypted with the specified customer-managed KMS key. This satisfies the requirement for automatic encryption of all new objects.

Answer

Use a lifecycle policy to apply encryption to existing objects.

Answer

Enable AWS CloudTrail to monitor encryption.

Question 14

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The primary instance fails, and automatic failover occurs. After failover, the data engineer notices that the new primary instance has a different DNS endpoint. Which TWO statements are true about this scenario? (Choose TWO.)

Accepted Answer

The DNS CNAME record is updated to point to the new primary.. When Amazon RDS performs automatic failover in a Multi-AZ deployment, it updates the DNS CNAME record for the primary DB instance to point to the new primary (formerly the standby). This ensures that applications using the original endpoint are transparently redirected to the new primary without manual intervention.

Answer

The standby instance is created in the same Availability Zone as the failed primary.

Answer

A manual DNS update is required to connect to the new primary.

Answer

The endpoint changes to the standby instance's endpoint.

Question 15

Refer to the exhibit. A data engineer is troubleshooting write throttling on the Orders table. The table has a composite primary key (OrderID as partition key, CustomerID as sort key). The engineer notices that writes are throttled even though the write capacity is not fully utilized. What is the most likely cause?

Accepted Answer

Writes are concentrated on a single partition key value.. D is correct because write throttling on an Amazon DynamoDB table occurs when requests exceed the provisioned throughput for a specific partition, even if the overall table write capacity is underutilized. With a composite primary key where OrderID is the partition key, writes concentrated on a single OrderID value (e.g., a hot key) will hit that partition's 3,000 WCU or 1,000 WCU (on-demand) limit, causing throttling while other partitions remain idle.

Answer

The table is empty and has no items.

Answer

A global secondary index (GSI) is consuming write capacity.

Answer

The read capacity units are too low.