DEA-C01 Data Store Management Practice Test 17 — 15 Questions

Question 1

A company runs a MySQL-compatible Amazon Aurora database for its e-commerce platform. The database experiences high write latency during peak hours. The application performs frequent INSERT and UPDATE operations on a table with 50 million rows. The DB instance is db.r5.large with 500 GB of Provisioned IOPS storage. A recent performance analysis shows that the average queue depth is consistently above 32 and write latency exceeds 50 ms. The company needs to reduce write latency without changing the application code. What should a data engineer do?

Accepted Answer

Resize the DB instance to a larger instance type such as db.r5.xlarge.. Option C is correct because the high queue depth (consistently above 32) and write latency exceeding 50 ms indicate that the current db.r5.large instance is CPU or I/O constrained for the write workload. Resizing to a larger instance type such as db.r5.xlarge increases the available vCPUs, memory, and network bandwidth, which directly reduces queue depth and write latency by allowing more concurrent write operations to be processed. This solution does not require application code changes and addresses the root cause of insufficient compute capacity for the frequent INSERT and UPDATE operations on the 50-million-row table.

Answer

Enable Aurora Auto Scaling to automatically add reader instances.

Answer

Convert the cluster to Aurora Serverless v2 to automatically scale compute capacity.

Answer

Create a read replica and configure the application to offload read queries.

Question 2

A media company stores video files in an Amazon S3 bucket with S3 Standard storage class. The files are accessed frequently for the first 30 days, then rarely after that. However, the company must be able to restore any deleted file within 7 days. The company wants to minimize storage costs while meeting the access and retention requirements. What should a data engineer do?

Accepted Answer

Use S3 Intelligent-Tiering and enable S3 Versioning on the bucket.. Option D is correct because S3 Intelligent-Tiering automatically moves objects between access tiers (frequent, infrequent, and archive instant access) based on changing access patterns, which minimizes storage costs for data with unknown or changing access patterns. Enabling S3 Versioning allows the company to restore any deleted file within 7 days by reverting to a previous version, meeting the retention requirement without additional cost for a separate backup.

Answer

Use S3 Standard-IA storage class from the start.

Answer

Use a lifecycle policy to transition objects to S3 One Zone-IA after 30 days.

Answer

Use S3 Glacier Deep Archive after 30 days and enable S3 Object Lock for retention.

Question 3

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 4

A company stores sensitive customer data in Amazon S3. The security team requires that all data be encrypted at rest using server-side encryption with AWS KMS managed keys (SSE-KMS). Which S3 bucket policy condition will enforce this requirement?

Accepted Answer

s3:x-amz-server-side-encryption-aws-kms-key-id. Option A is correct because the condition `s3:x-amz-server-side-encryption-aws-kms-key-id` enforces that objects uploaded to S3 must use a specific AWS KMS key for server-side encryption (SSE-KMS). This satisfies the security team's requirement that all data be encrypted at rest using SSE-KMS with AWS KMS managed keys, as it explicitly checks for the presence and value of the KMS key ID in the request.

Answer

s3:x-amz-server-side-encryption-customer-algorithm

Answer

s3:x-amz-server-side-encryption

Answer

s3:x-amz-server-side-encryption-aws-kms-key-id or s3:x-amz-server-side-encryption

Question 5

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'.. Option C is correct because 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 6

A data engineer needs to store semi-structured JSON logs from AWS CloudTrail. The logs are append-only and rarely accessed after 90 days. Which storage solution is MOST cost-effective?

Accepted Answer

Amazon S3 Glacier Deep Archive. Amazon S3 Glacier Deep Archive is the most cost-effective storage solution for CloudTrail logs that are append-only and rarely accessed after 90 days. It offers the lowest storage cost among AWS options (approximately $0.00099 per GB/month) and is designed for data that is accessed at most once or twice per year, with retrieval times of 12–48 hours. Since the logs are rarely accessed after 90 days, the retrieval latency is acceptable, and the cost savings over S3 Standard (which costs ~$0.023 per GB/month) are substantial.

Answer

Amazon S3 Standard

Answer

Amazon EBS with cold HDD volumes

Answer

Amazon DynamoDB with on-demand capacity

Question 7

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 8

A company is using AWS Glue to run ETL jobs that write data to an Amazon S3 data lake. The jobs are failing with '503 Slow Down' errors. The data engineering team has already implemented retries. What is the BEST long-term solution?

Accepted Answer

Implement a backoff strategy to reduce the request rate.. The '503 Slow Down' error from Amazon S3 indicates that the request rate is too high and S3 is throttling the requests. The best long-term solution is to implement a backoff strategy (exponential backoff) to reduce the request rate, which allows the Glue job to automatically slow down and retry with increasing delays, aligning with S3's request rate limits and avoiding sustained throttling.

Answer

Enable S3 Transfer Acceleration.

Answer

Use S3 multipart upload for all objects.

Answer

Increase the number of retries in the Glue job.

Question 9

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.. Option A is correct because Redshift Spectrum requires an external schema and table defined in the AWS Glue Data Catalog or an external Hive metastore. Option B is wrong because the data is already in S3. Option C is wrong because loading data into Redshift is not required for Spectrum. Option D is wrong because Spectrum does not require a separate cluster.

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 10

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 is automatically updated to point to the new primary instance in the standby Availability Zone. If the application is configured with the old primary instance's endpoint (the specific IP or DNS name of the original instance) instead of the RDS CNAME (which remains constant), it will attempt to connect to the failed instance, which is no longer available. This is the most likely cause of connectivity loss because the CNAME is the stable connection point that follows the active primary.

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 11

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. Option D is correct because LFU (Least Frequently Used) eviction policy evicts keys that are accessed least frequently, thus preserving frequently accessed keys. Option A is wrong because allkeys-lru evicts the least recently used keys, which may remove frequently accessed keys if they are not accessed recently. Option B is wrong because volatile-lru only applies to keys with TTL. Option C is wrong because noeviction will return errors when memory is full.

Answer

allkeys-lru

Answer

noeviction

Answer

volatile-lru

Question 12

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.. Options A and D are correct. Option A is correct because encrypting at rest with SSE-KMS provides encryption and key management. Option D is correct because S3 Block Public Access prevents accidental public exposure. Option B is wrong because S3 Transfer Acceleration is for speed, not security. Option C is wrong because cross-region replication does not protect data in the source bucket. Option E is wrong because Requester Pays does not control access.

Answer

Enable Requester Pays.

Answer

Enable S3 Transfer Acceleration.

Answer

Enable cross-region replication.

Question 13

A company is using Amazon Kinesis Data Streams to ingest real-time clickstream data. The data must be stored in Amazon S3 in near real-time with minimal overhead. Which THREE steps should the data engineer take to achieve this? (Choose THREE.)

Accepted Answer

Configure a Lambda function to transform data before delivery to S3.. Option A is correct because a Lambda function can be used as a data transformation step within a Kinesis Data Firehose delivery stream. This allows the clickstream data to be transformed (e.g., parsed, enriched, or reformatted) before being delivered to Amazon S3, enabling near real-time storage with minimal operational overhead.

Answer

Use Kinesis Data Analytics to process and store data in S3.

Answer

Enable S3 cross-region replication for the destination bucket.

Question 14

A company is evaluating Amazon DynamoDB for a new application. The application requires single-digit millisecond latency for read and write operations. Which TWO DynamoDB features should the company enable to achieve this? (Choose TWO.)

Accepted Answer

Use DAX with Write-Through caching.. Option A is correct because DAX with Write-Through caching ensures that every write to DynamoDB is also written to the DAX cache, so subsequent reads of the same item are served from the in-memory cache with single-digit millisecond latency. Option D is correct because DynamoDB Accelerator (DAX) is a fully managed, highly available, in-memory cache that reduces read response times from single-digit milliseconds to microseconds, directly meeting the latency requirement for read operations.

Answer

Enable DynamoDB Global Tables.

Answer

Enable DynamoDB Streams.

Answer

Enable auto-scaling for read and write capacity.

Question 15

The exhibit shows the lifecycle configuration for an S3 bucket. Objects in the bucket are 200 days old on average. What will happen to the objects?

Accepted Answer

Objects are in GLACIER now and will be deleted after 365 days from creation.. The lifecycle configuration shows a current version action to transition to GLACIOR (a misspelling of GLACIER) immediately (0 days after creation) and an expiration action to permanently delete the object 365 days after creation. Since the objects are already 200 days old on average, they have already been transitioned to GLACIER storage class. The expiration rule will delete them 365 days from their creation date, not from the current time.

Answer

Objects will be transitioned to GLACIER after 90 days and deleted after 365 days.

Answer

Objects will be transitioned to GLACIER after 200 days and deleted after 365 days.

Answer

Objects will be deleted after 90 days.