DEA-C01 Data Store Management Practice Test 13 — 15 Questions

Question 1

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

Accepted Answer

s3:x-amz-server-side-encryption-customer-key. Option C is correct because the condition key `s3:x-amz-server-side-encryption-customer-key` is specifically used to enforce that objects uploaded to S3 must use server-side encryption with customer-provided keys (SSE-C). This condition key checks for the presence of the `x-amz-server-side-encryption-customer-key` header in the request, which is required for SSE-C encryption. Without this header, the request is denied, ensuring all objects are encrypted at rest using customer-provided keys.

Answer

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

Answer

s3:x-amz-server-side-encryption

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

Question 2

A data engineer needs to store semi-structured JSON data for a real-time analytics application. The data will be queried using SQL-like statements and must support high-speed ingestion with minimal latency. Which AWS service is best suited for this use case?

Accepted Answer

Amazon Kinesis Data Analytics. Amazon Kinesis Data Analytics is best suited because it natively processes streaming JSON data using SQL-like statements (via Kinesis Data Analytics for SQL applications) with sub-second latency, enabling real-time analytics on semi-structured data without requiring a separate storage layer for ingestion. It directly integrates with Kinesis Data Streams or Firehose for high-speed ingestion and supports in-application queries on JSON payloads using the `json_extract` function or schema discovery.

Answer

Amazon S3

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Amazon Redshift

Answer

Amazon DynamoDB

Question 3

A company is running a MySQL database on Amazon RDS. The database size is 2 TB, and the company needs to migrate it to Amazon Aurora MySQL with minimal downtime. Which migration strategy is most appropriate?

Accepted Answer

Create an Aurora MySQL read replica from the RDS instance, then promote it.. Creating an Aurora MySQL read replica from the existing RDS MySQL instance allows the Aurora cluster to stay synchronized with the source using MySQL’s native binlog replication. Once the replica lag reaches zero, you can promote it to a standalone Aurora cluster with minimal downtime, typically just a few seconds to stop writes and redirect traffic. This approach avoids the lengthy export/import process and leverages Amazon’s managed replication for near-zero-downtime migration.

Answer

Use mysqldump to export the database and import it into Aurora.

Answer

Take a snapshot of the RDS instance and restore it as an Aurora cluster.

Answer

Use AWS Database Migration Service (DMS) with full load and ongoing replication.

Question 4

A data engineer notices that an Amazon Redshift cluster is experiencing slow query performance. The engineer suspects that tables are not properly sorted. Which diagnostic query should the engineer run to identify unsorted rows?

Accepted Answer

SELECT * FROM SVV_TABLE_INFO ORDER BY unsorted DESC;. The `SVV_TABLE_INFO` system view in Amazon Redshift provides metadata about each table, including the `unsorted` column which shows the percentage of unsorted rows. By ordering by `unsorted DESC`, the engineer can quickly identify tables with the highest proportion of unsorted data, which directly impacts query performance due to inefficient zone maps and scan pruning.

Answer

SELECT * FROM PG_CATALOG;

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SELECT * FROM STV_TBL_PERM;

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SELECT * FROM STL_LOAD_ERRORS;

Question 5

A company is using Amazon S3 as a data lake. The data engineer needs to ensure that all objects uploaded to a specific bucket are automatically replicated to a bucket in another AWS Region for disaster recovery. Which configuration should the engineer implement?

Accepted Answer

Enable S3 Cross-Region Replication (CRR) on the source bucket.. S3 Cross-Region Replication (CRR) is the correct choice because it automatically replicates objects from a source bucket in one AWS Region to a destination bucket in a different AWS Region, meeting the disaster recovery requirement for geographic separation. CRR requires versioning to be enabled on both buckets and replicates new objects asynchronously after upload.

Answer

Enable S3 Same-Region Replication (SRR) on the source bucket.

Answer

Use S3 Transfer Acceleration to copy objects to the destination.

Answer

Use S3 Batch Operations to copy existing objects.

Question 6

A company is using Amazon DynamoDB for a gaming application with high read and write throughput. The data engineer notices that the read latency is high during peak hours. The table has a partition key only (no sort key). The engineer wants to improve read performance by distributing reads across partitions more evenly. Which action should the engineer take?

Accepted Answer

Enable DynamoDB Accelerator (DAX).. Option C is correct because DynamoDB Accelerator (DAX) is an in-memory cache that reduces read latency from single-digit milliseconds to microseconds by caching frequently accessed items. Since the issue is high read latency during peak hours and the table has only a partition key, DAX offloads reads from the underlying table, distributing the read load and improving response times without changing the table's key structure.

Answer

Increase the read capacity units of the table.

Answer

Add a sort key to the table.

Answer

Enable DynamoDB global tables.

Question 7

A data engineer needs to store and analyze time-series data from IoT devices. The data volume is 10 GB per day, and the queries are mostly on the most recent 7 days of data. The engineer wants to minimize storage costs while retaining historical data for 1 year. Which combination of AWS services is most cost-effective?

Accepted Answer

Amazon Timestream. Amazon Timestream is purpose-built for time-series data, offering automatic tiering between in-memory (for recent 7 days) and magnetic stores (for historical data up to 1 year). This matches the query pattern (mostly recent 7 days) and retention requirement (1 year) while minimizing storage costs through its serverless, pay-per-query model. Timestream also supports time-series-specific functions like interpolation and smoothing, making it more efficient than general-purpose databases for this workload.

Answer

Amazon DynamoDB with TTL and S3 for archival

Answer

Amazon Redshift

Answer

Amazon RDS with MySQL

Question 8

A company is using Amazon EMR to process large datasets stored in Amazon S3. The data engineer wants to reduce the time it takes to read data from S3 by optimizing the data format. Which file format should the engineer recommend?

Accepted Answer

Parquet. Parquet is the correct choice because it is a columnar storage format that significantly reduces the amount of data read from Amazon S3 during analytical queries. By storing data column-wise, Parquet enables predicate pushdown and compression, which minimizes I/O and speeds up data processing in Amazon EMR, especially for large datasets.

Answer

CSV

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ORC

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JSON

Question 9

A company is using Amazon Redshift for data warehousing. The data engineer notices that the STL_ALERT_EVENT_LOG table shows many 'missing statistics' alerts. What is the best course of action to address this issue?

Accepted Answer

Run ANALYZE on the tables.. The STL_ALERT_EVENT_LOG table records alerts about query performance issues, including 'missing statistics' alerts. This indicates that the query optimizer lacks up-to-date table statistics, leading to suboptimal query plans. Running the ANALYZE command updates table statistics, enabling the optimizer to generate efficient execution plans. Therefore, option D is the correct course of action.

Answer

Increase the WLM concurrency slots.

Answer

Run VACUUM on the tables.

Answer

Enable compression on the tables.

Question 10

Which TWO options are valid ways to encrypt data at rest in Amazon S3? (Choose two.)

Accepted Answer

Server-Side Encryption with S3-Managed Keys (SSE-S3). Server-Side Encryption with S3-Managed Keys (SSE-S3) is a valid method for encrypting data at rest in Amazon S3 because it uses AES-256 encryption to automatically encrypt objects when they are written to S3 and decrypt them when accessed, with the encryption keys managed entirely by AWS. This option is correct as it directly addresses data at rest encryption within S3, requiring no client-side effort beyond setting the `x-amz-server-side-encryption` header to `AES256`.

Answer

Client-Side Encryption

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SSL/TLS Encryption

Answer

IAM Policy Encryption

Question 11

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

Accepted Answer

Offloads read traffic from the DynamoDB table.. Option A is correct because DAX acts as a read-through cache that offloads read traffic from the DynamoDB table, reducing the number of read requests that hit the underlying table and thus lowering the consumed read capacity units (RCUs). This allows the table to handle more concurrent reads without scaling up provisioned capacity.

Answer

Improves write throughput by batching writes.

Answer

Supports write-through caching to improve write performance.

Question 12

Which TWO actions can help improve query performance in Amazon Redshift? (Choose two.)

Accepted Answer

Use appropriate sort keys for tables.. Option A is correct because defining appropriate sort keys in Amazon Redshift enables the query optimizer to use zone maps to skip irrelevant data blocks during table scans, significantly reducing the amount of data read from disk. Sort keys also improve the effectiveness of merge joins and the performance of range-restricted queries by physically co-locating rows with similar sort key values on disk.

Answer

Disable SSL encryption for connections.

Answer

Use VARCHAR instead of CHAR for fixed-length strings.

Answer

Increase the number of nodes in the cluster.

Question 13

An IAM policy is attached to a user who tries to upload an object to the S3 bucket example-bucket using the AWS CLI without specifying the --server-side-encryption flag. What will happen?

Accepted Answer

The upload fails with an AccessDenied error.. The IAM policy denies s3:PutObject unless the request includes the `x-amz-server-side-encryption` header with a value of `AES256`. Since the user did not specify `--server-side-encryption` in the AWS CLI command, the request lacks this required header, causing S3 to evaluate the policy and return an AccessDenied error. The upload fails before any default encryption setting on the bucket is applied.

Answer

The upload succeeds and the object is encrypted with SSE-S3 by default.

Answer

The upload fails because the user does not have permission to use KMS.

Answer

The upload succeeds because the policy allows s3:PutObject.

Question 14

A company runs a real-time analytics platform on Amazon ECS that ingests streaming data from Amazon Kinesis Data Streams, processes it, and stores results in Amazon DynamoDB. The data volume spikes unpredictably, causing DynamoDB to throttle write requests. The application uses on-demand capacity mode. The data engineer notices that the throttling occurs on a specific partition due to a hot key. The hot key is a customer ID that receives a disproportionate number of writes. The application cannot change the partition key design immediately. The engineer needs to reduce throttling while maintaining low latency. Which solution is most effective?

Accepted Answer

Implement a write buffer using Amazon SQS, and have consumers write to DynamoDB at a controlled rate.. Option B is correct because buffering writes through Amazon SQS decouples the ingestion rate from DynamoDB's capacity, allowing consumers to write at a controlled pace. This directly mitigates throttling on the hot key without requiring a partition key redesign, and SQS provides low-latency, durable buffering suitable for real-time analytics.

Answer

Switch to provisioned capacity with auto scaling and increase the write capacity units.

Answer

Enable DynamoDB Accelerator (DAX) to cache the hot key writes.

Answer

Use DynamoDB Streams to trigger a Lambda function that retries throttled writes.

Question 15

A data engineer is responsible for a data warehouse on Amazon Redshift that stores 5 TB of data. The engineer needs to load 50 GB of new data daily from Amazon S3 into Redshift. The current load process uses the COPY command and takes 2 hours, which is within the maintenance window. However, the engineer wants to optimize the load time and reduce the impact on concurrent queries. The engineer notices that the tables are not distributed evenly across the slices. The cluster has 4 nodes of dc2.large. Which approach will best improve load performance?

Accepted Answer

Change the distribution style of the tables to EVEN.. Option B is correct because the COPY command distributes data across slices based on the table's distribution style. With dc2.large nodes, each node has 2 slices, so a 4-node cluster has 8 slices. If tables are not distributed evenly, some slices handle more data, causing bottlenecks. Changing the distribution style to EVEN forces rows to be spread uniformly across all slices, maximizing parallelism during the COPY load and reducing load time.

Answer

Increase the cluster size to 8 nodes.

Answer

Use GZIP compression on the S3 files.

Answer

Add sort keys to the tables based on the load timestamp.