DEA-C01 Data Store Management Practice Test 14 — 15 Questions

Question 1

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The database experiences intermittent slowdowns during peak hours. The company's DevOps team suspects that the primary instance is overwhelmed. Which action should the team take to distribute the read load without changing the application code?

Accepted Answer

Create a read replica and modify the connection string to point to the replica for read queries.. Creating a read replica and modifying the connection string to point to the replica for read queries (Option B) offloads read traffic from the primary RDS instance without requiring application code changes. This directly addresses the intermittent slowdowns during peak hours by distributing the read load, leveraging MySQL’s native replication to keep the replica synchronized. The key constraint is 'without changing the application code,' which is satisfied by simply updating the connection string in the application configuration.

Answer

Increase the instance size of the RDS instance.

Answer

Enable Multi-AZ on the existing instance.

Answer

Configure DynamoDB Accelerator (DAX) in front of the RDS instance.

Question 2

A data engineer is designing a data lake on Amazon S3. The data is ingested from multiple sources and stored in a partitioned structure under the 'landing' prefix. The engineer needs to ensure that only authorized applications can write to the 'landing' zone, while all AWS accounts in the organization can read the data. Which combination of S3 bucket policies and IAM policies should be used?

Accepted Answer

Create a bucket policy with a Deny for all principals except the authorized IAM roles on the 'landing' prefix. Add a separate statement allowing read access to the organization.. Option C is correct because it uses a bucket policy with an explicit Deny on the 'landing' prefix for all principals except the authorized IAM roles, ensuring only those roles can write. A separate Allow statement grants read access to the entire organization (e.g., via the `aws:PrincipalOrgID` condition key), which satisfies the requirement that all AWS accounts in the organization can read the data. This approach leverages S3 bucket policies for cross-account access control without relying on ACLs or IAM policies alone.

Answer

Use bucket ACLs to grant write access to the authorized IAM roles and read access to all authenticated users.

Answer

Use S3 Object Ownership to enforce bucket owner enforced. Grant write access via IAM roles.

Answer

Create an IAM policy that allows s3:PutObject only for the 'landing' prefix and attach it to the authorized roles. Allow read access via an S3 Access Point.

Question 3

A company uses Amazon DynamoDB as its primary data store for a web application. The application experiences high latency during peak hours. The data engineer notices that the table has a large number of items with the same partition key. Which DynamoDB feature should the engineer use to improve performance?

Accepted Answer

Redesign the partition key to use a composite key that includes a timestamp or random suffix.. The high latency is caused by a hot partition, where many items share the same partition key, overwhelming a single DynamoDB partition. Redesigning the partition key to include a timestamp or random suffix distributes the workload evenly across partitions, improving throughput and reducing latency. This directly addresses the root cause of the performance issue.

Answer

Enable DynamoDB Accelerator (DAX) to cache read requests.

Answer

Create a global table to replicate data across multiple Regions.

Answer

Enable auto scaling on the table to increase write capacity.

Question 4

A data engineer needs to store semi-structured JSON data that is accessed infrequently but must be retrievable within minutes. The data is generated by IoT devices and each object is about 500 KB. The engineer wants the most cost-effective storage solution. Which AWS service should be used?

Accepted Answer

Amazon S3 Standard-Infrequent Access (S3 Standard-IA). Amazon S3 Standard-Infrequent Access (S3 Standard-IA) is the correct choice because it is designed for data that is accessed infrequently but requires rapid retrieval (within minutes). The 500 KB JSON objects from IoT devices fit the use case, and S3 Standard-IA offers lower storage costs than S3 Standard while maintaining the same low-latency retrieval performance, making it the most cost-effective option for this scenario.

Answer

Amazon S3 Glacier Deep Archive

Answer

Amazon S3 Standard

Answer

Amazon Elastic Block Store (EBS)

Question 5

A company is migrating an on-premises PostgreSQL database to Amazon Aurora PostgreSQL. The database is 2 TB in size. The migration must have minimal downtime. Which approach should the data engineer use?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication to minimize downtime.. AWS DMS with ongoing replication (change data capture) is the correct approach because it allows a full load of the 2 TB database followed by continuous replication of changes from the on-premises PostgreSQL source to the Aurora PostgreSQL target, minimizing downtime to a short cutover window. This is the only option that supports near-zero downtime migration for large databases by capturing ongoing transactions.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and then copy data using S3.

Answer

Create an Aurora read replica from the on-premises database using native replication.

Answer

Use pg_dump to export the database and pg_restore to import into Aurora.

Question 6

A data engineer is designing a data store for a real-time analytics application that requires sub-millisecond read and write latency. The data is key-value in nature and the workload is both read-heavy and write-heavy. Which AWS service is most suitable?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the most suitable service because it is a fully managed NoSQL key-value and document database designed for single-digit millisecond latency at any scale, and with features like DynamoDB Accelerator (DAX) it can achieve sub-millisecond read latency. It supports both read-heavy and write-heavy workloads through its distributed architecture and auto-scaling capabilities, making it ideal for real-time analytics applications.

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Answer

Amazon S3

Question 7

A company uses Amazon Redshift for its data warehouse. The data engineer notices that queries are running slower than expected. The system administrator reports that the cluster's disk space is 80% full. Which action should the engineer take to improve query performance?

Accepted Answer

Add more nodes to the cluster to increase storage and compute capacity.. When a Redshift cluster's disk space is 80% full, query performance degrades because Redshift relies on large sequential I/O operations, and high disk utilization forces more random I/O and increases the likelihood of spilling to disk. Adding nodes increases both storage capacity and compute resources, directly alleviating the I/O bottleneck and improving query throughput. This is the recommended scaling action when disk space exceeds 70-80% utilization.

Answer

Redesign the sort keys to optimize query performance.

Answer

Run the VACUUM command to reclaim space.

Answer

Enable concurrency scaling to handle more queries.

Question 8

A data engineer is setting up an Amazon S3 bucket for storing sensitive financial data. The compliance team requires that all data be encrypted at rest using a customer-managed AWS KMS key. Additionally, the bucket must block public access. Which combination of settings should the engineer configure?

Accepted Answer

Enable default encryption with AWS-KMS and a customer managed key. Enable block public access settings.. Option A is correct because enabling default encryption with AWS-KMS using a customer-managed key ensures that all objects uploaded to the S3 bucket are automatically encrypted at rest with the required key type. Additionally, enabling block public access settings prevents any public access to the bucket, satisfying the compliance team's requirements.

Answer

Use S3 Object Ownership to enforce bucket owner enforced. Enable block public access.

Answer

Use S3 Bucket Keys to reduce KMS costs. Enable block public access.

Answer

Create a bucket policy that denies PutObject without encryption. Enable block public access.

Question 9

A data engineer needs to store log files from multiple applications in a centralized location. The logs are generated in JSON format and each log entry is about 1 KB. The engineer needs to query the logs occasionally using SQL-like queries. Which AWS service is most appropriate?

Accepted Answer

Amazon Athena with data stored in S3. Amazon Athena is the most appropriate service because it allows you to query log files stored in S3 directly using standard SQL, without needing to load or transform the data. Since the logs are in JSON format and each entry is about 1 KB, Athena's schema-on-read approach works perfectly for occasional SQL-like queries, and you only pay for the data scanned per query, making it cost-effective for infrequent access.

Answer

Amazon DynamoDB

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL

Question 10

A data engineer is designing a disaster recovery plan for an Amazon RDS for MySQL database. The database must be recoverable within 1 hour in a different AWS Region. Which TWO actions should the engineer take?

Accepted Answer

Create a cross-Region read replica.. A cross-Region read replica for Amazon RDS for MySQL provides a fully provisioned secondary database in a different AWS Region that can be promoted to a standalone primary in minutes, meeting the 1-hour recovery time objective (RTO). This approach ensures continuous replication from the source database, minimizing data loss and enabling rapid failover without manual snapshot management.

Answer

Enable Multi-AZ deployment.

Answer

Take manual snapshots and copy them to an S3 bucket in the other Region.

Answer

Use Amazon EventBridge to schedule snapshot copies.

Question 11

A company uses Amazon DynamoDB to store session data for a web application. The application experiences throttling during peak hours. The data engineer needs to reduce throttling. Which THREE actions should the engineer take?

Accepted Answer

Use DynamoDB Accelerator (DAX) to cache read requests.. DynamoDB Accelerator (DAX) is an in-memory cache that reduces read latency and offloads read requests from the DynamoDB table, directly decreasing the number of read capacity units consumed. By caching frequently accessed session data, DAX mitigates throttling during peak hours without requiring changes to the table's provisioned capacity.

Answer

Increase the provisioned read capacity units.

Answer

Enable auto scaling on the table.

Question 12

A data engineer is migrating a large Oracle data warehouse to Amazon Redshift. The engineer needs to ensure optimal performance. Which TWO practices should the engineer follow?

Accepted Answer

Choose appropriate sort keys based on common query patterns.. Option A is correct because Amazon Redshift uses sort keys to physically order data on disk, which allows the query optimizer to skip large blocks of data during scans via zone maps. Choosing sort keys based on common query patterns (e.g., range filters or frequent GROUP BY columns) dramatically reduces I/O and improves query performance, especially for large tables.

Answer

Design the schema as a normalized star schema with row-based storage.

Answer

Manually define compression encodings for each column.

Answer

Stage data in Amazon S3 before loading into Redshift.

Question 13

A company runs an e-commerce platform on AWS. The product catalog is stored in Amazon DynamoDB with a table that has a partition key of 'product_id' and a sort key of 'category'. The application frequently queries products by category and by product_id. Recently, the operations team noticed that read latency has increased significantly for queries that filter by category. The DynamoDB table has auto scaling enabled. The data engineer examines the CloudWatch metrics and sees that the ReadThrottleEvents metric is non-zero for the table, but the consumed read capacity is well below the provisioned limit. The table has a global secondary index (GSI) on the 'category' attribute. Which action is most likely to resolve the latency issue?

Accepted Answer

Redesign the GSI partition key to include a random suffix to distribute load across multiple partitions.. The issue is that the GSI on 'category' is experiencing hot partitions because 'category' has low cardinality, causing uneven data distribution. The non-zero ReadThrottleEvents on the GSI (not the main table) indicate throttling on the GSI's provisioned capacity, even though the main table's consumed read capacity is below its limit. Adding a random suffix to the GSI partition key distributes reads across multiple physical partitions, reducing hot spots and latency.

Answer

Switch the table to DynamoDB on-demand capacity mode.

Answer

Enable DynamoDB Accelerator (DAX) to cache read queries.

Answer

Increase the provisioned read capacity on the main table.

Question 14

A media company stores video metadata in Amazon RDS for PostgreSQL. The database is 500 GB and experiences high write traffic. The data engineer notices that the transaction log (WAL) is growing rapidly, causing storage issues. The company needs to retain backups for 30 days for compliance. The database is currently using automated backups with a retention period of 7 days. Which solution should the engineer implement to address the WAL growth while meeting compliance requirements?

Accepted Answer

Increase the backup retention period to 30 days.. Option C is correct because increasing the backup retention period to 30 days directly addresses the compliance requirement while also managing WAL growth. In Amazon RDS for PostgreSQL, automated backups rely on WAL files to support point-in-time recovery (PITR). When the retention period is too short (e.g., 7 days), RDS may not purge old WAL segments aggressively enough, causing them to accumulate. By extending the retention to 30 days, RDS properly manages WAL cleanup based on the new retention window, preventing unbounded WAL growth and meeting the 30-day compliance requirement.

Answer

Create manual snapshots daily and delete automated backups.

Answer

Change the instance type to a larger one with more storage.

Answer

Configure the database to stream WAL files to Amazon S3.

Question 15

A startup uses Amazon S3 to store user-uploaded images. The images are accessed frequently for the first week after upload, but after that they are rarely accessed. The company wants to optimize storage costs without compromising availability. The data engineer must implement a lifecycle policy to transition objects to a more cost-effective storage class after 30 days. The objects must be retrievable within minutes. Which storage class should the engineer transition the objects to?

Accepted Answer

S3 Standard-Infrequent Access. S3 Standard-Infrequent Access (S3 Standard-IA) is the correct choice because it offers a per-GB storage cost lower than S3 Standard while maintaining high durability (99.999999999%) and availability (99.9%), with retrieval times in milliseconds. The lifecycle policy transitions objects after 30 days, aligning with the access pattern where images are rarely accessed after the first week, and the requirement for retrieval within minutes is satisfied by S3 Standard-IA's instant access.

Answer

S3 One Zone-Infrequent Access

Answer

S3 Standard

Answer

S3 Glacier Instant Retrieval