DEA-C01 Data Store Management Practice Test 22 — 15 Questions

Question 1

A company is migrating a large Oracle database to Amazon Aurora PostgreSQL. The migration must have minimal downtime and preserve data consistency. Which THREE AWS services or features should be used?

Accepted Answer

AWS Schema Conversion Tool (SCT) for schema conversion. Option C (AWS Schema Conversion Tool) is correct because migrating from Oracle to Aurora PostgreSQL requires converting the Oracle schema, stored procedures, and PL/SQL objects into PostgreSQL-compatible DDL, which SCT automates. Option D (Amazon Aurora PostgreSQL as the target database) is correct because the scenario explicitly states the migration target is Aurora PostgreSQL, so the target engine must be Aurora PostgreSQL. Option E (AWS DMS for continuous replication) is correct because DMS supports ongoing change data capture (CDC) from Oracle to Aurora PostgreSQL, enabling minimal downtime by replicating changes until cutover. Option A is incorrect because RDS for Oracle is the source engine, not the target, and would not accomplish the migration to PostgreSQL. Option B is incorrect because AWS DataSync is a file/object transfer service for data like NFS/SMB/S3, not a database migration tool, and cannot preserve relational data consistency for an Oracle-to-PostgreSQL migration.

Answer

Amazon RDS for Oracle as the target

Answer

AWS DataSync for initial load

Question 2

A data engineer needs to store semi-structured JSON files that are accessed infrequently but must be retrievable within minutes. The data is immutable and must be stored cost-effectively. Which AWS service should the engineer use?

Accepted Answer

Amazon S3 with S3 Standard-IA storage class. Amazon S3 Standard-IA (Infrequent Access) is designed for data that is accessed less frequently but requires rapid retrieval when needed, with retrieval times in milliseconds. It offers lower storage costs than S3 Standard while maintaining high durability and availability, making it ideal for storing immutable semi-structured JSON files that must be retrievable within minutes. The service is cost-effective for infrequently accessed data because it charges a retrieval fee per GB, but the storage price is significantly lower than standard tiers.

Answer

Amazon DynamoDB with on-demand capacity

Answer

Amazon EBS with gp3 volume

Answer

Amazon RDS for PostgreSQL with JSONB data type

Question 3

A company runs an Apache Spark job on Amazon EMR that writes output to an S3 bucket. The job fails with the error 'S3AccessDeniedException' when writing the final output, but earlier stages succeed. The EMR cluster uses a service role and an instance profile. The S3 bucket policy allows access from the VPC only. What is the MOST likely cause?

Accepted Answer

The EMR cluster is not using a VPC endpoint for S3, so requests are denied by the bucket policy's VPC condition.. The bucket policy restricts access to requests originating from the VPC, typically using a condition like `aws:SourceVpc`. If the EMR cluster does not use a VPC endpoint for S3 (either Gateway or Interface endpoint), traffic from the cluster to S3 traverses the public internet and does not match the VPC condition, causing the `S3AccessDeniedException`. Earlier stages may succeed if they use cached data or different paths, but the final write fails because it hits the bucket policy check.

Answer

The S3 bucket uses SSE-C encryption, and the EMR cluster does not have the encryption key.

Answer

The EMR service role does not have permissions to write to the S3 bucket.

Answer

The S3 bucket is configured with 'Bucket owner enforced' setting for ACLs, and the EMR cluster's account is not the bucket owner.

Question 4

A data engineer is designing a data lake on Amazon S3. The data includes customer PII that must be encrypted at rest. The company also requires that the encryption keys be rotated automatically every year. Which encryption solution should the engineer use?

Accepted Answer

SSE-KMS with automatic key rotation enabled. SSE-KMS with automatic key rotation enabled meets both requirements: it encrypts data at rest in S3 and allows the company to automatically rotate the customer master key (CMK) every year. AWS KMS supports automatic annual rotation for symmetric CMKs, which satisfies the compliance need without manual intervention.

Answer

SSE-S3

Answer

SSE-C

Answer

Client-side encryption with AWS KMS

Question 5

A company needs to store application log files for 90 days for compliance. The logs are generated continuously and are rarely accessed after 30 days. The data engineer must minimize storage costs. Which storage solution should the engineer choose?

Accepted Answer

Amazon S3 Standard with a lifecycle policy to transition to S3 Standard-IA after 30 days and expire after 90 days. Amazon S3 Standard with a lifecycle policy to transition to S3 Standard-IA after 30 days and expire after 90 days is correct because it aligns with the access pattern: logs are frequently accessed only in the first 30 days, then rarely accessed for the remaining 60 days. S3 Standard-IA offers lower storage costs for infrequently accessed data while still providing millisecond retrieval, and the lifecycle policy automates the transition and eventual deletion, minimizing costs without sacrificing availability.

Answer

Amazon CloudWatch Logs with a retention policy of 90 days

Answer

Amazon S3 Glacier Deep Archive

Answer

Amazon EBS gp3 volumes attached to an EC2 instance

Question 6

A company is designing a data store for IoT sensor data that is written once and never updated. The data must be stored with high durability and low cost. Which TWO AWS storage services are most suitable? (Choose TWO.)

Accepted Answer

Amazon S3. Amazon S3 is correct because it provides 99.999999999% (11 9's) durability, is designed for write-once-read-many (WORM) workloads, and offers low-cost storage tiers suitable for IoT sensor data that is never updated. S3's object storage model and lifecycle policies allow automatic transition to colder storage, making it ideal for immutable data at scale.

Answer

Amazon ElastiCache

Answer

Amazon EBS

Answer

Amazon DynamoDB

Question 7

A data engineer applies the bucket policy shown in the exhibit to an S3 bucket. The bucket contains sensitive data that must be encrypted at rest and accessed only over HTTPS. Which of the following statements is true?

Accepted Answer

The policy enforces that all PutObject requests must include the x-amz-server-side-encryption header with value AES256.. The bucket policy includes a condition that denies PutObject requests unless the `s3:x-amz-server-side-encryption` header is present and set to `AES256`. This enforces server-side encryption with S3-managed keys (SSE-S3) for all uploads, ensuring data at rest is encrypted.

Answer

The policy allows both HTTP and HTTPS access.

Answer

The policy allows anonymous access to list objects in the bucket.

Answer

The policy requires the use of AWS KMS for server-side encryption.

Question 8

A company has an Amazon DynamoDB table with a provisioned write capacity of 1000 WCU. During a flash sale, the write traffic spikes to 5000 WCU for 10 minutes. The table is not auto-scaled. Which action should the data engineer take to handle the spike without throttling?

Accepted Answer

Convert the table to on-demand capacity mode before the sale.. The table is currently provisioned with 1000 WCU and cannot handle a spike to 5000 WCU. Converting to on-demand mode before the sale allows DynamoDB to automatically handle varying traffic without throttling, as on-demand capacity scales instantly to meet demand. Option D (auto-scaling) might not react quickly enough for a short 10-minute spike, and the table is not currently auto-scaled. Option C is incorrect because DAX is a read cache and does not buffer or improve write capacity. Option B is reactive and would not prevent initial throttling.

Answer

Set a CloudWatch alarm to increase provisioned capacity when write throttling occurs.

Answer

Use DynamoDB Accelerator (DAX) to cache writes.

Answer

Enable auto-scaling with a target utilization of 70% and a maximum capacity of 5000 WCU.

Question 9

A data engineer is designing a data lake on Amazon S3 and needs to ensure that objects are automatically encrypted at rest using server-side encryption with AWS KMS. Which bucket policy statement achieves this?

Accepted Answer

Deny PutObject requests where the x-amz-server-side-encryption header is not set to aws:kms.. It enforces server-side encryption with AWS KMS (SSE-KMS) by denying any PutObject request that does not include the `x-amz-server-side-encryption` header set to `aws:kms`. This bucket policy ensures that all objects written to the S3 bucket are automatically encrypted at rest using AWS KMS, meeting the requirement for mandatory encryption with a specific key management service.

Answer

Deny PutObject requests that do not include the x-amz-server-side-encryption header.

Answer

Deny PutObject requests where the x-amz-server-side-encryption header is not set to AES256.

Answer

Allow PutObject requests only if the x-amz-server-side-encryption header is set to AES256.

Question 10

A company uses Amazon Redshift for its data warehouse. The data engineer notices that queries are slow on a large table that is frequently filtered on a column 'transaction_date'. Which optimization technique best improves query performance?

Accepted Answer

Set the sort key to 'transaction_date'.. Setting the sort key to 'transaction_date' organizes the table data physically by that column, which allows Redshift to use zone maps to skip blocks that don't match query filters. This dramatically reduces the amount of data scanned for range-restricted queries on 'transaction_date', improving query performance.

Answer

Apply compression encoding to 'transaction_date'.

Answer

Set the distribution key to 'transaction_date'.

Answer

Run VACUUM on the table.

Question 11

A data engineer is migrating an on-premises MongoDB database to Amazon DocumentDB. Which migration strategy minimizes downtime?

Accepted Answer

Use AWS DMS with full load and ongoing replication from MongoDB to DocumentDB.. AWS DMS with full load and ongoing replication (change data capture) minimizes downtime by continuously synchronizing changes from the source MongoDB to the target DocumentDB after the initial full load, allowing a cutover with only a brief pause. This is the only option that supports near-zero downtime migration for live databases.

Answer

Take a snapshot of the MongoDB database and restore it to DocumentDB.

Answer

Use AWS Database Migration Service (AWS DMS) with full load only.

Answer

Export data using mongodump and import using mongorestore.

Question 12

A company needs to store files that are accessed by multiple EC2 instances in a VPC. The files must be concurrently accessible and durable. Which storage solution should the data engineer choose?

Accepted Answer

Amazon Elastic File System (Amazon EFS). Amazon EFS provides a fully managed, scalable, and elastic NFS file system that can be concurrently accessed by multiple EC2 instances across multiple Availability Zones. It is designed for high durability (11 nines of durability) and automatically replicates data across multiple AZs within a region, meeting the requirements for concurrent access and durability.

Answer

Amazon EC2 instance store

Answer

Amazon Simple Storage Service (Amazon S3)

Answer

Amazon Elastic Block Store (Amazon EBS)

Question 13

Which TWO actions are recommended for securing data at rest in Amazon S3? (Choose two.)

Accepted Answer

Enable default encryption on the S3 bucket using SSE-S3 or SSE-KMS.. Option A is correct because enabling default bucket encryption with SSE-S3 or SSE-KMS ensures that every object written to the bucket is automatically encrypted at rest, satisfying the core requirement for data-at-rest protection in Amazon S3. Option D is correct because a bucket policy that denies PutObject requests lacking the x-amz-server-side-encryption header enforces encryption on upload, preventing unencrypted objects from being stored even if default encryption is bypassed or misconfigured. Option B is not a security control; S3 Bucket Key reduces AWS KMS request costs and CloudTrail event volume but does not itself secure data at rest. Option C addresses availability and data durability against accidental deletion through versioning, not encryption at rest. Option E provides geographic redundancy and disaster recovery via cross-region replication, but replication does not encrypt data at rest by itself.

Answer

Use S3 Bucket Key to reduce KMS request costs.

Answer

Enable S3 Versioning to protect against accidental deletions.

Answer

Configure cross-region replication to replicate data to another bucket.

Question 14

A data engineer needs to store JSON documents that are accessed by a serverless application using AWS Lambda. The documents are frequently updated and need low latency (single-digit milliseconds) for read and write operations. Which AWS service should the engineer use?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is a fully managed NoSQL key-value and document database that provides single-digit millisecond latency for read and write operations at any scale. It natively supports JSON documents, integrates directly with AWS Lambda via the AWS SDK, and handles frequent updates efficiently through its auto-scaling and on-demand capacity modes, making it ideal for serverless applications requiring low-latency data access.

Answer

Amazon ElastiCache for Redis

Answer

Amazon S3 (with S3 Select)

Answer

Amazon RDS for MySQL

Question 15

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.