DEA-C01 Practice Questions

Question 1

An e-commerce company uses Amazon DynamoDB as the primary data store for its product catalog. The table has a simple primary key (ProductID) and handles 10,000 writes per second during peak hours. Recently, the engineering team noticed increased write latency and throttled requests during peak times. The table's provisioned write capacity is set to 12,000 WCU. What is the most likely cause of the throttling?

Accepted Answer

Write traffic is unevenly distributed across partitions. DynamoDB partitions data by the primary key's hash value. If write traffic is unevenly distributed across partitions (e.g., a few ProductIDs receive most writes), those hot partitions can exceed their individual throughput limits (3,000 WCU per partition for provisioned tables), causing throttling even when the table's total provisioned WCU of 12,000 is not fully utilized.

Answer

The table has reached the maximum number of partitions

Answer

DynamoDB Accelerator (DAX) is not configured

Answer

A global secondary index is consuming write capacity

Question 2

A data engineer is designing a data lake on Amazon S3. Which feature should be used to manage the lifecycle of objects and move them to cheaper storage classes automatically?

Accepted Answer

S3 Lifecycle policies. S3 Lifecycle policies are the correct feature for automatically managing object lifecycles and transitioning objects to cheaper storage classes (e.g., from S3 Standard to S3 Glacier Deep Archive) based on age or other rules. This directly meets the requirement to move objects to cost-optimized storage without manual intervention.

Answer

S3 Object Lock

Answer

S3 Storage Class Analysis

Answer

S3 Inventory

Question 3

A company needs to ingest data from an on-premises database to Amazon S3 with minimal impact on the source database. The data volume is several TB. Which AWS service is best suited for this task?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is best suited because it can continuously replicate data from an on-premises database to Amazon S3 with minimal impact on the source. DMS uses change data capture (CDC) to capture only incremental changes after an initial full load, avoiding heavy read loads on the source database. This makes it ideal for migrating several TB of data while keeping the source operational.

Answer

AWS Direct Connect

Answer

AWS Snowball Edge

Answer

Amazon S3 Transfer Acceleration

Question 4

Order the steps to migrate an on-premises database to Amazon RDS using AWS DMS.

Accepted Answer

Step 1: Create a replication instance. Step 2: Configure source and target endpoints. Step 3: Create a migration task. Step 4: Start the migration task. Step 5: Validate the migrated data.. First, create the replication instance. Then configure endpoints, create the migration task, start it, and finally validate the migrated data.

Answer

Step 1: Configure source and target endpoints. Step 2: Create a replication instance. Step 3: Create a migration task. Step 4: Start the migration task. Step 5: Validate the migrated data.

Answer

Step 1: Create a replication instance. Step 2: Create a migration task. Step 3: Configure source and target endpoints. Step 4: Start the migration task. Step 5: Validate the migrated data.

Answer

Step 1: Create a replication instance. Step 2: Configure source and target endpoints. Step 3: Start the migration task. Step 4: Create a migration task. Step 5: Validate the migrated data.

Question 5

A data engineer needs to ingest on-premises CSV files into Amazon S3 every hour. The files are less than 1 GB each. Which service is the most cost-effective and requires the least operational overhead?

Accepted Answer

AWS DataSync. AWS DataSync is the most cost-effective and least overhead option for scheduled, recurring transfers of on-premises CSV files to S3. It provides a simple agent-based setup, supports hourly scheduling, and handles files under 1GB efficiently without complex configuration. In contrast, Amazon Kinesis Data Firehose is designed for streaming data ingestion, not batch file transfers; AWS Snowball Edge is intended for large-scale offline data migrations, not hourly incremental transfers; and AWS Database Migration Service (DMS) is specialized for migrating databases, not file transfers.

Answer

Amazon Kinesis Data Firehose

Answer

AWS Snowball Edge

Answer

AWS Database Migration Service (DMS)

Question 6

A company is using Amazon S3 to store sensitive customer data. The security team requires that all data be encrypted in transit and at rest. Additionally, they want to prevent any accidental public access. Which combination of actions should the data engineer take?

Accepted Answer

Enable default encryption with SSE-S3, enforce HTTPS only via bucket policy, and enable S3 Block Public Access.. Enabling default encryption with SSE-S3 ensures data is encrypted at rest automatically, enforcing HTTPS only via bucket policy ensures encryption in transit by rejecting HTTP requests, and enabling S3 Block Public Access prevents any accidental public exposure regardless of bucket policies or ACLs. This combination satisfies all security requirements: encryption in transit, encryption at rest, and prevention of public access.

Answer

Enable default encryption with SSE-KMS, allow both HTTP and HTTPS, and set bucket ACLs to private.

Answer

Use client-side encryption, enforce HTTPS via bucket policy, and enable S3 Block Public Access.

Answer

Enable default encryption with SSE-S3, allow HTTP and HTTPS, and use bucket ACLs to block public access.

Question 7

A company is using AWS DMS to replicate data from an on-premises Oracle database to Amazon RDS for MySQL. The replication is working, but the target table has a different schema. Which DMS feature should be used to transform the source schema to match the target?

Accepted Answer

Use DMS transformation rules. AWS DMS transformation rules allow you to modify the schema, table, or column names and data types during the migration process. This feature is specifically designed to handle schema transformations within the DMS task itself, enabling you to map the source Oracle schema to the target MySQL schema without external tools or services.

Answer

Use AWS Schema Conversion Tool (SCT)

Answer

Use AWS Glue ETL jobs

Answer

Use AWS Lambda triggers

Question 8

An IAM policy includes the above resource ARN for CloudWatch Logs. A data engineer needs to allow a Lambda function to create log streams and put logs to the log group 'my-log-group'. However, the Lambda function is failing with access denied. What is the issue?

Accepted Answer

The ARN does not include the log-stream portion.. The ARN provided in the policy is for the log group itself (arn:aws:logs:region:account-id:log-group:my-log-group), but CloudWatch Logs requires separate permissions for the log-stream subresource. To allow a Lambda function to create log streams and put logs, the ARN must include the log-stream portion, typically with a wildcard like arn:aws:logs:region:account-id:log-group:my-log-group:log-stream:*. Without this, the IAM policy does not grant access to the log-stream actions (CreateLogStream, PutLogEvents), causing an access denied error even if the log group ARN is correct.

Answer

The region in the ARN does not match the Lambda function's region.

Answer

The Lambda function does not have an execution role.

Answer

The ARN is incorrectly formatted because of the wildcard.

Question 9

A data engineer is designing a data ingestion pipeline for real-time clickstream data from a website. The data must be ingested with low latency (seconds) and made available for multiple consumer applications, including a dashboard that refreshes every minute and a machine learning model that processes data in near-real-time. The engineer needs to choose a streaming ingestion service. Which TWO services meet these requirements? (Select TWO.)

Accepted Answer

Amazon Managed Streaming for Apache Kafka (Amazon MSK). Amazon Kinesis Data Streams (C) provides sub-second ingestion latency and supports multiple consumer applications via its enhanced fan-out feature, enabling a dashboard and ML model to consume data concurrently with low latency. Amazon MSK (B) offers similar real-time capabilities with Apache Kafka's native pub/sub model, allowing multiple consumers to process the same stream independently and with low latency, meeting the near-real-time requirements.

Answer

Amazon Kinesis Data Firehose

Answer

Amazon Simple Queue Service (SQS)

Answer

Amazon S3

Question 10

A company uses AWS Glue to run ETL jobs daily. The data is stored in S3 as Parquet files partitioned by date. Recently, jobs have failed with the error 'No such file or directory' for certain partitions. What is the MOST likely cause?

Accepted Answer

A partition folder was deleted or not created by the upstream process.. The error 'No such file or directory' indicates that the Glue ETL job is attempting to read a specific S3 partition path that does not exist. Since the data is partitioned by date and the job runs daily, the most likely cause is that the upstream process failed to create or accidentally deleted the partition folder for that date. Glue's dynamic frame or Spark DataFrame will throw this error when it tries to list or read files from a missing prefix.

Answer

The schema has changed and Glue cannot parse the data.

Answer

The files are compressed with an unsupported codec.

Answer

The IAM role does not have s3:GetObject permission.

Question 11

A data engineering team notices that an AWS Glue ETL job, which processes hourly data from an S3 bucket, is taking progressively longer to run. The job reads Parquet files partitioned by date and hour. Which action is MOST likely to improve the job's performance?

Accepted Answer

Enable pushdown predicate filtering on the job's data source.. Pushdown predicate filtering allows AWS Glue to push filter conditions down to the data source, so only the relevant partitions and rows are read from S3. Since the data is partitioned by date and hour, predicate pushdown minimizes the amount of data scanned, reducing I/O and improving job performance. This is especially effective for Parquet, which supports columnar pruning and predicate pushdown.

Answer

Convert Parquet files to CSV to improve read performance.

Answer

Increase the number of DPUs for the job.

Answer

Switch from Spark to Python shell for simpler processing.

Question 12

A company uses an Amazon RDS for MySQL DB instance with Multi-AZ deployment. The primary DB instance fails unexpectedly. What happens to the database endpoint?

Accepted Answer

The existing endpoint continues to work and automatically points to the standby DB instance.. In a Multi-AZ RDS deployment, the DNS endpoint remains unchanged during a failover. When the primary DB instance fails, Amazon RDS automatically updates the DNS record to point to the standby instance in the other Availability Zone. This ensures the application can continue using the same endpoint without any manual intervention, providing high availability.

Answer

A new endpoint is created for the standby and the application must use the new endpoint.

Answer

The database becomes unavailable until the primary is restored from a snapshot.

Answer

The existing endpoint is deleted and a new endpoint is provided after manual DNS update.

Question 13

A data engineer is troubleshooting an issue where an Amazon Redshift query returns an error: 'ERROR:  permission denied for relation table_name'. The user has been granted SELECT on the table. What is the most likely cause?

Accepted Answer

The user does not have USAGE permission on the schema.. In Amazon Redshift, to access a table, a user must have USAGE permission on the schema containing the table, in addition to SELECT or other table-level permissions. Without USAGE on the schema, the user receives a 'permission denied for relation' error even if SELECT is granted. Option D is correct. Option A (session timeout) would cause a different error or disconnection. Option B (no CONNECT permission) would prevent connecting to the database. Option C (wrong schema) would result in a 'schema not found' error, not a permission denied error.

Answer

The user's session has timed out.

Answer

The user does not have CONNECT permission on the database.

Answer

The table is in a different schema than expected.

Question 14

A company has an Amazon RDS for MySQL database that is experiencing performance issues due to a large number of read requests. The application is read-heavy and can tolerate eventually consistent reads. Which action will reduce the load on the primary database with the least operational overhead?

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 to a read-only copy, which directly addresses the read-heavy workload. Since the application can tolerate eventually consistent reads, the slight replication lag is acceptable, and this solution requires minimal operational overhead—just a few clicks in the AWS console or a single API call—without any application code changes.

Answer

Use Amazon ElastiCache for caching

Answer

Enable Multi-AZ deployment

Answer

Increase the instance size of the primary DB

Question 15

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

Accepted Answer

Offloads read traffic from the DynamoDB table.. 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.

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