DEA-C01 Practice Test 12 — 15 Questions

Question 1

A data engineer is troubleshooting an Amazon Redshift cluster that is running out of disk space. The engineer runs STV_PARTITIONS and notices that some slices have significantly more data than others. What is the most likely cause and solution?

Accepted Answer

Data distribution skew due to uneven distribution style; change distribution style to EVEN or correct KEY. B is correct because STV_PARTITIONS shows per-slice disk usage, and significant variation indicates data distribution skew. Uneven distribution causes some slices to fill faster, leading to premature disk-full errors. Changing the distribution style to EVEN (for tables without join keys) or correcting the KEY distribution style (using a high-cardinality, evenly distributed column) rebalances data across slices.

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Poorly chosen sort keys; redefine sort keys

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Some nodes are underutilized; add more nodes

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Concurrency scaling is disabled; enable concurrency scaling

Question 2

A company uses Amazon S3 as its data lake. A data engineer needs to enforce encryption of data at rest using server-side encryption with AWS KMS. Which S3 bucket property should be configured?

Accepted Answer

Default encryption. Option A is correct because configuring default encryption on an S3 bucket ensures that all objects stored in the bucket are encrypted at rest using server-side encryption. When AWS KMS is specified as the encryption type, S3 automatically encrypts objects with a KMS key (SSE-KMS) upon upload, even if the upload request does not include encryption headers. This enforces encryption at rest without requiring changes to client applications.

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Server access logging

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Versioning

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Bucket policy

Question 3

A data engineer notices that an Amazon Redshift cluster’s storage usage is increasing rapidly due to many UPDATE and DELETE operations. The engineer needs to reclaim storage space and improve query performance. Which action should be taken?

Accepted Answer

Run VACUUM command. The VACUUM command in Amazon Redshift reclaims disk space occupied by deleted or updated rows and re-sorts the data according to the table's sort keys. This directly addresses the storage increase from UPDATE/DELETE operations and improves query performance by restoring the physical order of rows, which reduces the number of blocks scanned.

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UNLOAD the table to S3 and reload

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Increase cluster node count

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Run ANALYZE command

Question 4

A data engineer needs to store semi-structured JSON transaction logs for analytics. The logs are written once and rarely accessed. The storage must be cost-effective. Which AWS service should be used?

Accepted Answer

Amazon S3. Amazon S3 is the correct choice because it provides highly durable, cost-effective object storage ideal for semi-structured JSON transaction logs that are written once and rarely accessed. S3's lifecycle policies can automatically transition such infrequently accessed data to S3 Glacier or S3 Glacier Deep Archive for even lower storage costs, making it the most economical option for this use case.

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Amazon DynamoDB

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Amazon RDS

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Amazon Redshift

Question 5

A data engineer is designing a multi-Region disaster recovery solution for an Amazon DynamoDB table. The table must be available in a secondary Region with minimal data loss and automatic failover. Which feature should be used?

Accepted Answer

DynamoDB global tables. DynamoDB global tables provide a fully managed, multi-Region, multi-active database solution that replicates data automatically across selected AWS Regions. This ensures automatic failover with eventual consistency and minimal data loss, meeting the disaster recovery requirements for high availability and automatic failover without manual intervention.

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DynamoDB on-demand backup and restore in the secondary Region

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DynamoDB point-in-time recovery (PITR)

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DynamoDB cross-Region snapshot export to S3

Question 6

A company stores log files in Amazon S3. They want to automatically move logs older than 90 days to S3 Glacier Deep Archive to reduce costs. Which S3 feature should be used?

Accepted Answer

S3 Lifecycle configuration. S3 Lifecycle configuration allows you to define rules that automatically transition objects to colder storage classes, such as S3 Glacier Deep Archive, based on age. By setting a rule to move objects older than 90 days to S3 Glacier Deep Archive, you reduce storage costs without manual intervention. This is the correct feature for automating tier-based data lifecycle management.

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S3 Intelligent-Tiering

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S3 Replication

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S3 Object Lock

Question 7

A data engineer needs to monitor Amazon DynamoDB table metrics to detect throttled requests. Which CloudWatch metric should the engineer set an alarm on?

Accepted Answer

ThrottledRequests. Option C is correct because `ThrottledRequests` is the specific Amazon CloudWatch metric that tracks the number of requests to a DynamoDB table that are throttled due to exceeding the provisioned throughput capacity. This metric directly reflects throttling events, making it the appropriate choice for setting an alarm to detect throttled requests.

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ReadThrottleEvents

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SuccessfulRequestLatency

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ConsumedWriteCapacityUnits

Question 8

A company uses Amazon Redshift for a data warehouse. They notice that queries are slow due to heavy data skew. Which optimization technique should be applied first?

Accepted Answer

Set an appropriate distribution style. Data skew occurs when rows are distributed unevenly across Redshift slices, causing some nodes to process far more data than others. Setting an appropriate distribution style (e.g., KEY, EVEN, or ALL) redistributes the data to balance the workload, directly addressing the root cause of the slowness. This is the first optimization to apply because skew is a fundamental distribution issue that other tuning steps cannot fix.

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Configure workload management (WLM) queues

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Define sort keys on frequently filtered columns

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Apply compression encodings to columns

Question 9

A data engineer is troubleshooting a failed AWS Glue Crawler. The crawler logs show 'Insufficient permissions to access S3 bucket'. What should the engineer do to resolve this?

Accepted Answer

Update the IAM role used by the crawler to include S3 read permissions. The AWS Glue Crawler uses an IAM role to access data sources. The error 'Insufficient permissions to access S3 bucket' indicates that the IAM role attached to the crawler lacks the necessary S3 read permissions (e.g., s3:GetObject, s3:ListBucket). Updating the IAM role's policy to include these permissions resolves the issue, as the crawler operates under that role, not under a specific IAM user.

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Grant the crawler's IAM user access to the bucket

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Attach a VPC endpoint to the S3 bucket

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Enable S3 default encryption on the bucket

Question 10

A company has an S3 bucket with millions of objects. The data engineer needs to identify which objects are not accessed for 90 days to move them to a lower-cost storage class. Which feature should be used?

Accepted Answer

S3 Storage Class Analysis. S3 Storage Class Analysis (SCA) is the correct feature because it monitors access patterns across objects and provides recommendations for transitioning data to lower-cost storage classes based on last-access dates. SCA can analyze objects that have not been accessed for 90 days and generate a report to inform lifecycle policy creation, directly addressing the requirement to identify objects for cost optimization.

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S3 Inventory

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S3 Server Access Logs

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S3 Event Notifications

Question 11

A company has an Amazon Redshift cluster that stores petabytes of data. Queries are experiencing high disk usage due to large intermediate results. The data engineer needs to improve query performance without adding more nodes. Which action should the engineer take?

Accepted Answer

Apply column compression encoding to reduce data size.. Option C is correct because compression reduces data size on disk and can improve query performance by reducing I/O. Option A is wrong because sort keys affect order, not intermediate result size. Option B is wrong because distribution keys affect data distribution, not intermediate results directly. Option D is wrong because WLM queues manage concurrency, not disk usage.

Answer

Set appropriate distribution keys to minimize data movement.

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Configure workload management (WLM) queues to limit concurrency.

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Define sort keys on all columns used in WHERE clauses.

Question 12

A company uses Amazon DynamoDB for a gaming leaderboard. The table has a primary key of GameId (partition key) and Score (sort key). The application needs to retrieve the top 10 scores for a given game. Which strategies can improve query performance? (Choose TWO.)

Accepted Answer

Create a global secondary index with Score as sort key. Option B is correct because creating a global secondary index (GSI) with Score as the sort key allows efficient range queries on scores for a given GameId. DynamoDB can then use the GSI to retrieve the top 10 scores in sorted order without scanning the entire table, leveraging the index's sort key to fetch only the highest values.

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Change the primary key to a single attribute

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Use a Scan operation with a limit

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Increase the write capacity units

Question 13

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.

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

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Use S3 Transfer Acceleration to copy objects to the destination.

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Use S3 Batch Operations to copy existing objects.

Question 14

A data engineer notices that an Amazon Redshift cluster's storage utilization has grown unexpectedly. The cluster uses automatic compression and has a mix of fact and dimension tables. The engineer runs VACUUM and ANALYZE, but storage does not decrease. Which action is most likely to reduce storage consumption?

Accepted Answer

Perform a DEEP COPY on the largest tables.. Option A is correct because DEEP COPY recreates the table with a fresh, optimally sorted and compressed storage layout, reclaiming space that VACUUM alone cannot recover. In Redshift, VACUUM reorganizes and reclaims space from deleted rows but does not re-apply compression or rebuild the underlying storage blocks; DEEP COPY (e.g., using CREATE TABLE AS or the DEEP COPY command) physically rewrites the data, eliminating fragmentation and applying the current compression encoding, which can significantly reduce storage consumption when automatic compression has left suboptimal encodings or when historical updates have bloated the table.

Answer

Run VACUUM with the BOOST option.

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Run ANALYZE with the FULL keyword on all tables.

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Modify the sort key on the largest tables to a more selective column.

Question 15

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The database experiences intermittent slowdowns during peak hours. The company's DevOps team suspects that the primary instance is overwhelmed. Which action should the team take to distribute the read load without changing the application code?

Accepted Answer

Create a read replica and modify the connection string to point to the replica for read queries.. Creating a read replica and modifying the connection string to point to the replica for read queries (Option B) offloads read traffic from the primary RDS instance without requiring application code changes. This directly addresses the intermittent slowdowns during peak hours by distributing the read load, leveraging MySQL’s native replication to keep the replica synchronized. The key constraint is 'without changing the application code,' which is satisfied by simply updating the connection string in the application configuration.

Answer

Increase the instance size of the RDS instance.

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Enable Multi-AZ on the existing instance.

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Configure DynamoDB Accelerator (DAX) in front of the RDS instance.