DEA-C01 Timed Practice Test 2 — 10 Questions

Question 1

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?

10 minute time limit — choose an answer to begin.

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 2

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 3

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 4

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 5

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.

Question 6

A data engineer needs to encrypt data in transit between an Amazon RDS for MySQL instance and an application. Which solution should be used?

Accepted Answer

Use SSL/TLS to connect to the RDS instance. Encryption in transit for an RDS for MySQL instance is achieved by connecting with SSL/TLS, which encrypts the wire protocol between the application and the database. RDS MySQL supports TLS and provides an rds-ca certificate that the client uses to verify the server. Enabling SSL/TLS on the connection is the direct, correct answer for data in transit.

Answer

Enable encryption at rest using AWS KMS

Answer

Store the data in Amazon S3 with server-side encryption

Answer

Use AWS CloudHSM to generate and store encryption keys

Question 7

Refer to the exhibit. A data engineer has attached this bucket policy to an S3 bucket named data-lake-bucket. The engineer wants to allow only GET requests from the corporate network (10.0.0.0/16) over HTTPS. However, users report that they cannot access objects even when connected to the corporate network. What is the issue?

Accepted Answer

The Deny statement blocks all requests that are not using HTTPS, including those from the corporate network.. The Deny statement with `aws:SecureTransport` set to `false` blocks all HTTP requests. Since the Allow statement only permits GET requests from the corporate network (10.0.0.0/16) but does not require HTTPS, any request from that network that uses HTTP is denied by the explicit Deny. The Deny statement overrides the Allow, so even legitimate corporate users are blocked if they use HTTP.

Answer

The Deny statement should include a condition on the source IP.

Answer

The Allow statement should include a condition for SecureTransport.

Answer

The Allow statement should specify s3:GetObject instead of s3:GetObject.

Question 8

A company is using AWS Glue to catalog data stored in Amazon S3. The data is partitioned by year, month, and day. A data analyst reports that new partitions are not automatically discovered by the Glue crawler. The crawler runs on a schedule every hour. What is the MOST likely reason for the missing partitions?

Accepted Answer

The IAM role used by the crawler does not have permission to list the S3 bucket.. For a Glue crawler to discover new partitions in S3, its IAM role must have s3:ListBucket (and GetObject) permissions on the bucket and prefix. If the role lacks ListBucket, the crawler cannot enumerate the partition folders and will silently miss new partitions even though it runs on schedule. This is the most common cause of 'crawler runs but doesn't find new data' issues.

Answer

The Glue Data Catalog is not configured to use a Hive metastore.

Answer

The number of partitions exceeds the Glue catalog limit of 100,000.

Answer

The crawler schedule is set to run too frequently.

Question 9

A company is migrating a legacy data warehouse to Amazon Redshift. They need to choose a distribution style to minimize data movement during joins. Which THREE factors should they consider?

Accepted Answer

The size of the table (number of rows).. Option A is correct because table size (number of rows) is a primary driver of distribution style choice: small tables are typically assigned ALL distribution so they can be broadcast to every node, eliminating data movement during joins, while large tables need KEY or EVEN distribution. Option B is correct because the whole purpose of choosing a distribution style is to co-locate matching rows on the same slice; if a table is frequently joined on a specific column, distributing both tables on that join key keeps the join local and avoids network redistribution. Option D is correct because fact and dimension tables play different roles in a star schema: large fact tables are usually distributed on their most common join key (or EVEN), while smaller dimension tables are often set to ALL so they are replicated to every node and can be joined without movement. Option C is not a factor because the number of columns does not affect how rows are distributed across slices; it only affects storage width and I/O, not join data movement. Option E is not a factor because Redshift supports distribution keys of various data types, and the data type itself does not determine whether a join requires redistribution — what matters is whether the joined columns match and are used as distribution keys.

Answer

The number of columns in the table.

Answer

The data type of the distribution key column.

Question 10

A company uses Amazon Kinesis Data Streams to ingest clickstream data. The data is consumed by a custom consumer application that writes to Amazon S3 every 5 minutes. The consumer is falling behind and processing lag is increasing. Which action is MOST effective to reduce the lag?

Accepted Answer

Increase the number of shards in the Kinesis stream. The consumer is falling behind because the stream's throughput capacity is insufficient for the incoming data volume. Increasing the number of shards in the Kinesis stream directly increases the total read capacity (each shard provides 2 MB/s read throughput and 5 transactions/second), allowing the consumer to process more data in parallel and reduce lag.

Answer

Switch to Amazon Kinesis Data Firehose to deliver data directly to S3

Answer

Increase the batch size of records written to S3

Answer

Reduce the retention period of the stream