DEA-C01 Data Store Management Practice Test 21 — 15 Questions

Question 1

Which TWO of the following are features of Amazon RDS Multi-AZ deployments? (Choose 2.)

Accepted Answer

Automatic failover to a standby instance in case of an AZ failure.. Amazon RDS Multi-AZ deployments automatically handle failover to a standby instance in a different Availability Zone when the primary instance fails or the AZ becomes unavailable. This synchronous replication ensures zero data loss and minimal downtime, with the standby instance automatically promoted to primary without manual intervention.

Answer

Read replicas in the same region for offloading read traffic.

Answer

Automatic storage scaling based on usage.

Answer

Synchronous replication across AWS Regions.

Question 2

An IAM policy is attached to a role assumed by authenticated users via Amazon Cognito. What does this policy allow?

Accepted Answer

Users can read items in the Orders table only if the partition key matches their Cognito identity ID.. The policy uses a condition key like `dynamodb:LeadingKeys` with a value referencing `${cognito-identity.amazonaws.com:sub}`. This restricts DynamoDB actions to items where the partition key matches the user's Cognito identity ID, ensuring fine-grained access control. Option D correctly states that users can read items only when the partition key equals their identity ID, which is the intended behavior for row-level security.

Answer

Users can read and write items in the Orders table where the partition key matches their Cognito identity ID.

Answer

Users can read any item in the Orders table using GetItem and Query.

Answer

Users can scan the entire Orders table but only if they use a filter expression.

Question 3

A data engineer runs the above command and gets the output. What does the 'MFADelete' setting imply?

Accepted Answer

To permanently delete a version of an object, the user must provide MFA.. The 'MFADelete' setting on an S3 bucket versioning configuration requires multi-factor authentication to permanently delete an object version. This means that when a user issues a DELETE request with a version ID (a permanent delete), they must include a valid MFA token in the request headers. It does not apply to creating new versions, reading objects, or other operations.

Answer

Any modification to an object requires MFA.

Answer

MFA is required for all read operations as well.

Answer

All operations on the bucket require MFA authentication.

Question 4

A data engineer runs the above DDL statement in Amazon Athena. The query returns an error. What is the most likely cause?

Accepted Answer

The INPUTFORMAT is incorrect for Parquet files.. The DDL statement uses the default INPUTFORMAT 'org.apache.hadoop.mapred.TextInputFormat', which is designed for text-based files like CSV or JSON, not for binary columnar formats like Parquet. Parquet requires 'org.apache.hadoop.hive.ql.io.parquet.MapredParquetInputFormat' to correctly read the file's metadata and compressed column chunks. Using the wrong INPUTFORMAT causes Athena to fail when attempting to parse the Parquet file, resulting in an error.

Answer

The SerDe is not compatible with Parquet files.

Answer

The S3 bucket location does not exist.

Answer

The table name contains underscores.

Question 5

A company uses Amazon S3 to store sensitive data. The security team wants to ensure that all objects uploaded to a specific S3 bucket are automatically encrypted at rest using server-side encryption with AWS KMS managed keys (SSE-KMS). Which bucket policy statement should be added to enforce this requirement?

Accepted Answer

Deny put requests where 's3:x-amz-server-side-encryption' is not 'aws:kms'. It denies any S3 PUT request that does not include the `x-amz-server-side-encryption` header set to `aws:kms`, thereby enforcing SSE-KMS encryption for all objects uploaded to the bucket. This bucket policy condition ensures that only requests specifying AWS KMS-managed keys are allowed, meeting the security team's requirement for automatic encryption at rest with SSE-KMS.

Answer

Deny put requests where 's3:x-amz-server-side-encryption' is 'aws:kms'

Answer

Deny put requests where 's3:x-amz-server-side-encryption' is not 'AES256'

Answer

Deny put requests where 's3:x-amz-server-side-encryption' is not set

Question 6

A data engineering team is designing a data lake on Amazon S3. They need to store raw data in a format that supports schema evolution and is optimized for analytics with Amazon Athena. Which storage format should they use?

Accepted Answer

Parquet. Parquet is the correct choice because it is a columnar storage format that is highly optimized for Amazon Athena, which can read only the necessary columns to minimize data scanned and reduce query costs. Parquet also supports schema evolution through features like nested data structures and the ability to add or remove columns without rewriting the entire dataset, making it ideal for raw data lakes that must accommodate changing schemas over time.

Answer

CSV

Answer

Avro

Answer

JSON

Question 7

A company runs a MySQL database on Amazon RDS. The database size is 500 GB and is experiencing high read traffic. The team wants to improve read performance with minimal operational overhead. Which action should they take?

Accepted Answer

Create a read replica in the same region. Creating a read replica in the same region offloads read traffic from the primary RDS instance by providing a separate, read-only copy of the database. This directly addresses high read traffic with minimal operational overhead, as RDS manages the asynchronous replication using MySQL's native binlog-based replication. The replica can serve SELECT queries, reducing load on the primary instance without requiring application changes.

Answer

Enable Multi-AZ deployment

Answer

Implement Amazon ElastiCache for caching

Answer

Upgrade to a larger instance class

Question 8

A data engineer needs to transfer 10 TB of data from an on-premises Hadoop cluster to Amazon S3. The network bandwidth is limited to 100 Mbps, and the transfer must be completed within 48 hours. Which solution meets the requirements?

Accepted Answer

Use AWS Snowball Edge device to transfer data offline. The on-premises Hadoop cluster has 10 TB of data to transfer, but the network bandwidth is only 100 Mbps. At 100 Mbps, the theoretical maximum transfer rate is about 12.5 MB/s, which would take approximately 10 TB / 12.5 MB/s ≈ 800,000 seconds ≈ 222 hours — far exceeding the 48-hour window. AWS Snowball Edge is an offline, physical device that bypasses network constraints entirely, allowing you to transfer the data by shipping the device, which completes within days regardless of bandwidth.

Answer

Use AWS DataSync to transfer data online

Answer

Use S3 Transfer Acceleration over the internet

Answer

Set up AWS Direct Connect to increase bandwidth

Question 9

A company has an Amazon DynamoDB table with on-demand capacity mode. The table stores session data for a web application. Recently, the application experienced throttling errors during a traffic spike. The team wants to prevent future throttling while optimizing costs. What should they do?

Accepted Answer

Implement a DynamoDB Accelerator (DAX) cluster. A DynamoDB Accelerator (DAX) cluster provides an in-memory cache that absorbs read-heavy traffic spikes, reducing the number of read requests that reach the underlying DynamoDB table. Since the throttling errors occurred during a traffic spike and the table uses on-demand capacity, which already scales automatically for writes and reads, the bottleneck is likely read-heavy traffic overwhelming the table's throughput. DAX offloads reads from the table, preventing throttling without requiring any changes to capacity mode, and it is cost-effective because it reduces read capacity unit consumption.

Answer

Enable DynamoDB auto scaling on the table

Answer

Switch to provisioned capacity with auto scaling

Answer

Increase the read and write capacity of the table

Question 10

A data engineer needs to store JSON documents that are frequently accessed by a low-latency web application. The data does not require complex queries, and the access pattern is primarily by a key. Which AWS service is most appropriate?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the most appropriate service because it is a fully managed NoSQL key-value and document database designed for single-digit millisecond latency at any scale. It natively supports JSON documents and provides fast, consistent access by primary key without requiring complex query capabilities, making it ideal for low-latency web applications.

Answer

Amazon ElastiCache for Redis

Answer

Amazon S3

Answer

Amazon RDS for MySQL

Question 11

A company uses Amazon Redshift for data warehousing. The data team notices that queries are slow due to high disk usage on the cluster. They need to free up space without deleting any data. What should they do?

Accepted Answer

Run a deep copy to re-sort and reclaim space. A deep copy recreates the table with optimal sort order and reclaims unused space by reorganizing data blocks. This process effectively frees up disk space without deleting any data, addressing the high disk usage issue.

Answer

Change the table's sort keys

Answer

Run VACUUM command

Answer

Add more nodes to the cluster

Question 12

A financial services company stores sensitive transaction data in an Amazon S3 bucket. Compliance requires that all objects be encrypted using SSE-KMS and that the bucket be protected from accidental deletion. Which combination of actions meets these requirements? (Select TWO.)

Accepted Answer

Add a bucket policy that denies PutObject if the object is not encrypted with SSE-KMS. A bucket policy with a condition denying PutObject unless the object's encryption status matches SSE-KMS (using the s3:x-amz-server-side-encryption-aws-kms-key-id condition key) enforces encryption at the upload level. This ensures that any object written to the bucket must be encrypted with a KMS key, meeting the compliance requirement.

Answer

Enable MFA Delete on the bucket

Answer

Enable S3 Block Public Access

Answer

Set default encryption to SSE-S3

Question 13

A startup is building a mobile application that requires a database to store user profiles and preferences. The database must scale automatically with minimal administration. Which AWS service should they use?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is a fully managed NoSQL key-value and document database that delivers single-digit millisecond performance at any scale. It supports automatic scaling of throughput capacity and storage with no downtime, making it ideal for a mobile application that requires minimal administrative overhead. The serverless, pay-per-request billing model aligns perfectly with the startup's need for automatic scaling and low operational burden.

Answer

Amazon Redshift

Answer

Amazon Aurora

Answer

Amazon RDS for PostgreSQL

Question 14

Which TWO actions can improve query performance on an Amazon Redshift cluster? (Choose two.)

Accepted Answer

Define appropriate sort keys. Defining appropriate sort keys in Amazon Redshift physically orders data on disk by the sort key columns, enabling the query optimizer to use zone maps to skip large blocks of data that do not match query predicates. This drastically reduces the amount of data scanned, especially for range-restricted queries, improving I/O and overall query performance.

Answer

Increase the number of nodes

Answer

Use EVEN distribution style for all tables

Answer

Run VACUUM command regularly

Question 15

Which THREE factors should a data engineer consider when choosing between Amazon S3 and Amazon DynamoDB for storing time-series data? (Choose three.)

Accepted Answer

Required query complexity (simple key lookups vs. range scans). Amazon S3 supports range scans via its ListObjectsV2 API with prefix and delimiter parameters, but it is not optimized for complex queries like filtering on non-key attributes or aggregations. DynamoDB, on the other hand, excels at simple key lookups and range scans on its sort key, but lacks native support for complex query patterns such as multi-attribute filtering or joins. Therefore, the required query complexity directly influences the choice: S3 is better for simple prefix-based scans, while DynamoDB is better for key-value lookups and sort-key range queries.

Answer

Cost per GB of storage

Answer

Total data volume