DEA-C01 Data Store Management Practice Test 28 — 15 Questions

Question 1

A company uses Amazon Kinesis Data Firehose to deliver streaming data to an Amazon S3 bucket. The data is JSON and each record is about 2 KB. The delivery stream is configured to buffer incoming data to 5 MB or 60 seconds, whichever comes first. The data engineering team notices that the S3 bucket contains many small files (average 2 MB), which makes subsequent processing inefficient. They need to reduce the number of small files without increasing the latency beyond 5 minutes. Which solution should they implement?

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

Accepted Answer

Increase the buffer size to 50 MB and the buffer interval to 300 seconds.. Increasing the buffer size to 50 MB and the buffer interval to 300 seconds directly addresses the root cause: the current 5 MB buffer size triggers a flush too frequently, producing many 2 MB files. By raising the buffer size to 50 MB, each flush will contain more data, resulting in larger S3 objects (up to ~50 MB uncompressed), while the 300-second interval ensures latency stays within the 5-minute requirement. This reduces the number of small files without requiring additional services or post-processing.

Answer

Enable compression (GZIP) on the delivery stream.

Answer

Use a Lambda function to merge small files after delivery.

Answer

Decrease the buffer size to 1 MB and the buffer interval to 60 seconds.

Question 2

A company is migrating an on-premises MySQL database to Amazon RDS for MySQL. The database is 500 GB and has a 24/7 uptime requirement. The migration must minimize downtime. Which approach should be used?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication to migrate the data.. AWS DMS with ongoing replication (change data capture) allows you to perform a full load of the 500 GB database and then continuously replicate changes from the on-premises MySQL source to the Amazon RDS target. This minimizes downtime because you can cut over to RDS in seconds after the target is synchronized, rather than taking the source offline for an extended period.

Answer

Take a snapshot of the on-premises database, convert it to a volume, and restore to RDS.

Answer

Export the database using mysqldump and import it into RDS using mysql command.

Answer

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

Question 3

A company is using Amazon DynamoDB with on-demand capacity for a gaming application. During a new game launch, write traffic spikes to 50,000 writes per second, but the application experiences throttling. The DynamoDB table has a partition key of 'game_id' and a sort key of 'timestamp'. What is the MOST likely cause of throttling?

Accepted Answer

Hot partitions due to a skewed access pattern on the partition key 'game_id'.. DynamoDB on-demand capacity automatically scales to handle traffic spikes, but it still has per-partition throughput limits. With 'game_id' as the partition key, a single popular game can create a hot partition where all writes target the same partition, exceeding the partition's maximum write capacity (1,000 write capacity units per partition) and causing throttling, even though the overall table capacity is sufficient.

Answer

The table has not enabled auto-scaling for writes.

Answer

The table's on-demand capacity is insufficient for the write spike.

Answer

The sort key is not optimal for write-heavy workloads.

Question 4

A company uses Amazon Redshift for data warehousing. The data engineering team notices that queries are slow due to high disk I/O. The team wants to improve query performance without changing the cluster configuration. Which action should the team take?

Accepted Answer

Redesign tables with appropriate sort keys and distribution styles.. Redesigning tables with appropriate sort keys and distribution styles directly addresses high disk I/O by minimizing data scanning and reducing data movement across nodes. Sort keys enable Redshift to skip irrelevant blocks via zone maps, while distribution styles (KEY, ALL, EVEN) optimize data locality for joins and aggregations, reducing I/O without changing cluster configuration.

Answer

Increase the number of nodes in the cluster.

Answer

Run the ANALYZE command to update table statistics.

Answer

Run the VACUUM command to reclaim disk space.

Question 5

A company wants to use Amazon Redshift Spectrum to query data in Amazon S3. The data is in Parquet format and partitioned by date. Which step is required to enable Redshift Spectrum?

Accepted Answer

Create an external schema and external table in the AWS Glue Data Catalog.. Redshift Spectrum allows querying data directly in Amazon S3 without loading it into Redshift. To use Spectrum, you must define an external schema and external table in the AWS Glue Data Catalog (or an external Hive metastore) that points to the S3 location and specifies the Parquet format and partition structure. This enables Redshift to read the data in place using the Spectrum engine.

Answer

Load the data into Redshift tables using the COPY command.

Answer

Create a separate Redshift Spectrum cluster.

Answer

Copy the data from S3 to Redshift-managed storage.

Question 6

A company is using Amazon RDS for PostgreSQL with Multi-AZ deployment. The primary instance fails and a failover occurs. After the failover, the application cannot connect to the database. What is the MOST likely cause?

Accepted Answer

The application is using the old primary instance endpoint instead of the RDS CNAME.. After a Multi-AZ failover in Amazon RDS for PostgreSQL, the DNS CNAME record automatically updates to point to the new primary instance in the standby Availability Zone. If the application hardcodes the old primary instance's endpoint (specific IP or DNS name) instead of using the RDS CNAME (which remains constant), it will attempt to connect to the failed instance, causing connectivity loss. The CNAME is the stable connection point that always resolves to the current primary instance.

Answer

The database instance is in a 'stopped' state after failover.

Answer

The Multi-AZ failover requires manual intervention to complete.

Answer

The security group for the RDS instance was not updated during failover.

Question 7

A company is using Amazon ElastiCache for Redis to cache frequently accessed data. The cache hit ratio is low, and the engineering team suspects that the eviction policy is causing important data to be removed. Which eviction policy should be used to minimize eviction of the most frequently accessed keys?

Accepted Answer

allkeys-lfu. The allkeys-lfu (Least Frequently Used) eviction policy is the correct choice because it explicitly tracks and retains keys that are accessed most frequently across the entire keyspace. Since the cache hit ratio is low due to eviction of important data, LFU ensures that frequently accessed keys are evicted last, directly addressing the problem of important data being removed.

Answer

allkeys-lru

Answer

noeviction

Answer

volatile-lru

Question 8

A company is designing a data lake on Amazon S3 for analytics. The data includes sensitive personally identifiable information (PII). Which TWO actions should the company take to protect the data? (Choose TWO.)

Accepted Answer

Enable S3 Block Public Access.. S3 Block Public Access (Option A) prevents any public access to S3 buckets and objects, which is critical for protecting PII from unintended exposure. Default encryption with SSE-KMS (Option E) ensures that all data written to S3 is encrypted at rest using AWS KMS-managed keys, providing both encryption and centralized key management for sensitive data.

Answer

Enable Requester Pays.

Answer

Enable S3 Transfer Acceleration.

Answer

Enable cross-region replication.

Question 9

An IAM role 'DataLakeRole' has the above S3 bucket policy attached to an S3 bucket. The role is assumed by an AWS Glue job. The Glue job is failing with 'Access Denied' errors when trying to list objects in the bucket. Which action should be added to the policy to fix the issue?

Accepted Answer

Add s3:ListBucket action for the bucket ARN (arn:aws:s3:::my-data-lake).. The Glue job is failing with 'Access Denied' when trying to list objects, which requires the s3:ListBucket permission on the bucket itself (not on objects). Option B correctly adds s3:ListBucket for the bucket ARN (arn:aws:s3:::my-data-lake), which grants permission to list the contents of the bucket. Without this action, even if other permissions exist, the ListObjectsV2 API call used by AWS Glue to enumerate objects will be denied.

Answer

Add s3:ListObjects action for the bucket ARN.

Answer

Add s3:GetObjectVersion action for the object ARN.

Answer

Add s3:ListBucket action for the object ARN (arn:aws:s3:::my-data-lake/*).

Question 10

A data engineer needs to store JSON documents that are frequently updated and require ACID transactions. Which AWS database service is most appropriate?

Accepted Answer

Amazon DocumentDB. Amazon DocumentDB (with MongoDB compatibility) is the correct choice because it is a fully managed document database designed to store, query, and index JSON-like documents. It supports multi-document ACID transactions, providing atomicity, consistency, isolation, and durability for frequently updated JSON documents. DocumentDB also offers a MongoDB-compatible API, making it a natural fit for JSON document workloads. While Amazon DynamoDB supports ACID transactions via TransactWriteItems and TransactGetItems and can store JSON-like items, it is primarily a key-value and document store with a different data model and is not the AWS service purpose-built for general-purpose JSON document storage with complex querying and multi-document transactions. Amazon Neptune is a graph database, and Amazon S3 is object storage without ACID transactional semantics, so neither is appropriate.

Answer

Amazon Neptune

Answer

Amazon DynamoDB

Answer

Amazon S3

Question 11

A company is using Amazon RDS for MySQL and needs to reduce read latency for a global user base. Which AWS feature should be implemented?

Accepted Answer

Read Replicas. Amazon RDS Read Replicas allow you to offload read traffic from the primary DB instance to one or more read-only copies, which can be placed in different AWS Regions to reduce read latency for a global user base. Unlike Multi-AZ, which is designed for high availability, Read Replicas directly address read performance and latency by distributing read queries closer to users. Cross-Region Replication for RDS MySQL is achieved through Read Replicas, making option C the correct choice for reducing read latency globally.

Answer

Multi-AZ deployment

Answer

Aurora Auto Scaling

Answer

Cross-Region Replication

Question 12

A company has an Amazon S3 bucket with versioning enabled. They want to automatically delete noncurrent versions of objects after 30 days. Which lifecycle rule action should be used?

Accepted Answer

NoncurrentVersionExpiration. The NoncurrentVersionExpiration lifecycle action is specifically designed to remove noncurrent object versions after a specified number of days. Since versioning is enabled and the requirement is to delete noncurrent versions after 30 days, this action directly meets the goal without affecting current versions or other lifecycle aspects.

Answer

Expiration

Answer

NoncurrentVersionTransition

Answer

AbortIncompleteMultipartUpload

Question 13

A data engineer is designing a data lake on Amazon S3. The data is frequently accessed by multiple analytics services, and the company needs to enforce fine-grained access control based on data tags. Which combination of AWS services should be used?

Accepted Answer

AWS Lake Formation with tag-based access control. AWS Lake Formation with tag-based access control (TBAC) is the correct choice because it provides fine-grained, attribute-based access control (ABAC) at the column, row, and cell level across a data lake on S3. By assigning LF-tags to Data Catalog resources and defining permissions based on those tags, you can enforce granular access policies that scale without managing individual user-to-resource mappings. This directly meets the requirement for tag-driven, fine-grained access for multiple analytics services.

Answer

S3 Block Public Access settings

Answer

S3 Access Points with bucket policies

Answer

S3 Object Lambda with IAM policies

Question 14

Which TWO of the following are benefits of using Amazon DynamoDB Accelerator (DAX)? (Choose TWO.)

Accepted Answer

Provides microsecond read latency. Option B is correct because DAX is an in-memory write-through cache placed in front of DynamoDB that serves eventually consistent reads from RAM, delivering microsecond read latency for cached items instead of the single-digit millisecond latency of direct DynamoDB reads. Option C is correct because read requests that hit the DAX cache are answered by DAX itself, so they never reach the DynamoDB table, which offloads read traffic and reduces the read capacity units consumed on the underlying table. Option A is not correct because DAX does not accelerate writes: write operations are still written through to DynamoDB synchronously, so write throughput and write latency remain governed by the table. Option D is not correct because durability across Availability Zones is provided by DynamoDB's own multi-AZ replication of table data, not by DAX, which is a cache and can lose cached data. Option E is not correct because DAX does not reduce the storage consumed by the DynamoDB table; it is an additional caching layer that itself incurs cost.

Answer

Improves write throughput

Answer

Provides data durability across Availability Zones

Answer

Reduces storage costs

Question 15

Which THREE of the following are valid storage classes in Amazon S3? (Choose THREE.)

Accepted Answer

S3 Standard. S3 Standard (A) is a valid storage class designed for frequently accessed data with low latency and high throughput, and it is the default class for S3 objects. S3 Intelligent-Tiering (C) is a valid class that automatically moves objects between access tiers based on changing access patterns, charging a small monitoring and automation fee. S3 One Zone-IA (E) is a valid class that stores data in a single Availability Zone at lower cost, intended for infrequently accessed data that can be easily recreated. The other options are not real S3 storage classes: S3 Archive (B) does not exist — the archival class is S3 Glacier, and S3 Cold (D) is not a class either, as the closest real classes are S3 Glacier Instant Retrieval and S3 Glacier Flexible Retrieval.

Answer

S3 Archive

Answer

S3 Cold