DEA-C01 Data Store Management Practice Test 20 — 15 Questions

Question 1

A data engineer is designing a data lake on Amazon S3. The data is accessed frequently for the first 30 days, then rarely accessed after 90 days, and must be archived after 1 year. Which S3 lifecycle policy configuration meets these requirements with the lowest cost?

Accepted Answer

Transition to S3 Standard-IA after 30 days, then to S3 Glacier Deep Archive after 365 days.. Option B is correct because it transitions to S3 Standard-IA after 30 days (cost-effective for infrequent access) and to S3 Glacier Deep Archive after 365 days (lowest cost archival). Option A transitions to S3 One Zone-IA, which is not recommended for durability. Option C transitions to S3 Glacier Flexible Retrieval, which costs more than Deep Archive. Option D transitions to S3 Glacier Instant Retrieval, which is expensive for archival.

Answer

Transition to S3 One Zone-IA after 30 days, then to S3 Glacier Deep Archive after 365 days.

Answer

Transition to S3 Glacier Flexible Retrieval after 90 days.

Answer

Transition to S3 Glacier Instant Retrieval after 30 days, then expire after 365 days.

Question 2

A company uses Amazon Redshift for its data warehouse. The data engineering team notices that queries against a large fact table are slow. The table is distributed using DISTSTYLE EVEN and has multiple sort keys. After analyzing the query plans, they find that most queries filter on a specific column, 'customer_id'. Which change would most likely improve query performance for these filter operations?

Accepted Answer

Change to DISTSTYLE KEY on the 'customer_id' column.. Option C is correct because using DISTSTYLE KEY on 'customer_id' collocates rows with the same customer_id on the same slice, reducing data shuffling for queries filtering on that column. Option A (EVEN distribution) does not help with filtering. Option B (ALL distribution) is for small dimension tables. Option D (compound sort key with other columns) may not help if the filter is only on 'customer_id'.

Answer

Add a secondary sort key on 'customer_id'.

Answer

Change to DISTSTYLE EVEN with a different sort key.

Answer

Change to DISTSTYLE ALL for the fact table.

Question 3

A data engineer needs to migrate an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB and has a continuous stream of write operations. The migration should minimize downtime. Which AWS service should be used?

Accepted Answer

AWS Database Migration Service (DMS). Option B is correct because AWS DMS supports ongoing replication from on-premises PostgreSQL to RDS, allowing minimal downtime. Option A (S3) is for bulk data transfer. Option C (Snowball) is for offline data transfer, not for ongoing replication. Option D (Glue) is for ETL, not for database migration with replication.

Answer

AWS DataSync

Answer

AWS Snowball Edge

Answer

AWS Glue

Question 4

A company uses Amazon DynamoDB for a gaming application. The table has a partition key of 'user_id' and a sort key of 'game_timestamp'. The application frequently queries by 'user_id' and filters by 'game_timestamp' within a specific date range. The queries are slow. The table has a global secondary index (GSI) on 'game_timestamp'. What is the most likely cause of the slow queries?

Accepted Answer

A hot partition exists due to uneven access pattern on 'user_id'.. Option B is correct because querying by 'user_id' using the base table is efficient, but if the GSI is being used for queries that filter by 'game_timestamp' without the partition key, the GSI may not be designed optimally. However, the stem says queries are by 'user_id' and filter by 'game_timestamp' – that should use the base table. Option A is not likely because sort key filtering is efficient. Option C (hot partition) is possible if 'user_id' distribution is skewed. Option D (GSI write capacity) doesn't affect reads. The most likely cause is a hot partition due to uneven 'user_id' distribution.

Answer

The GSI has insufficient read capacity.

Answer

The GSI is used instead of the base table for queries on 'user_id'.

Answer

The sort key is not used in the query.

Question 5

A data engineer needs to store semi-structured JSON data that is accessed infrequently but requires millisecond retrieval latency. The data is immutable once written. Which AWS service is most cost-effective?

Accepted Answer

Amazon S3 (Standard-IA) with S3 Select. Option A is correct because S3 with S3 Select can retrieve specific JSON fields with low latency for infrequent access, and Standard-IA reduces cost. Option B (DynamoDB) is for frequent access patterns. Option C (RDS) is for relational data. Option D (ElastiCache) is for caching, not durable storage.

Answer

Amazon DynamoDB with on-demand capacity

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for PostgreSQL with JSONB

Question 6

A company runs a critical application on Amazon RDS for MySQL. To ensure high availability and automatic failover, the database is deployed as a Multi-AZ DB instance. The application uses read-heavy workloads. Which additional configuration should be used to offload read traffic without impacting write performance?

Accepted Answer

Create one or more Read Replicas in different AZs.. Option C is correct because Read Replicas can serve read traffic and reduce load on the primary instance, while Multi-AZ provides high availability. Option A (Multi-AZ for reads) does not offload reads; the standby is not used for reads. Option B (single AZ with larger instance) does not provide high availability. Option D (ElastiCache) caches data but does not serve read replicas for complex queries.

Answer

Use the Multi-AZ standby instance for read queries.

Answer

Use Amazon ElastiCache to cache read queries.

Answer

Change to a Single-AZ deployment with a larger instance size.

Question 7

A data engineer is troubleshooting an Amazon Redshift cluster that has been experiencing slow query performance. The engineer checks the system tables and finds that many queries are waiting on 'wlm_queued' time. The cluster has 10 nodes and uses automatic WLM. What is the most likely cause?

Accepted Answer

The number of concurrent queries exceeds the available query slots.. Option D is correct because 'wlm_queued' time indicates queries are waiting for a slot in a queue, often due to concurrency scaling limits or insufficient queue slots. With automatic WLM, the number of concurrent queries is limited by the number of slices (usually 2 per node, so 20 concurrent queries). If many queries are submitted, they queue. Option A (disk) would show disk-related waits. Option B (network) would show network waits. Option C (sort) would show sort-related waits.

Answer

Network bandwidth saturation between nodes.

Answer

Sorting operations are too expensive.

Answer

Insufficient disk space on the cluster.

Question 8

A company uses Amazon S3 to store large datasets. The data engineering team needs to provide access to specific objects in the bucket to external partners using presigned URLs. Each URL should expire after 12 hours. The team wants to ensure that the presigned URLs cannot be used to access other objects in the bucket. Which approach should be taken?

Accepted Answer

Generate presigned URLs using the AWS SDK, specifying the exact object key and expiration time.. Option A is correct because a presigned URL generated for a specific object key and expiration time limits access to that object only. Option B (IAM role) is for internal use. Option C (bucket policy with IP restriction) is not per-object. Option D (CloudFront signed URLs) also works but is more complex and may not be necessary.

Answer

Create an IAM role for each partner and attach a policy that grants access to specific objects.

Answer

Use a bucket policy that allows access only from the partner's IP address range.

Answer

Use CloudFront signed URLs with a custom policy that restricts access to specific objects.

Question 9

Which TWO of the following are valid approaches to implement fine-grained access control for Amazon DynamoDB items based on user attributes? (Choose 2.)

Accepted Answer

Use Amazon Cognito identity pools with IAM roles that include conditions based on user attributes.. Option C is correct because Amazon Cognito identity pools can be configured to assume IAM roles with fine-grained policies that use condition keys such as `dynamodb:LeadingKeys` or custom attribute-based conditions. This allows access to DynamoDB items to be restricted based on user-specific attributes (e.g., user ID) without hardcoding permissions per user.

Answer

Enable row-level security in DynamoDB using AWS Lake Formation.

Answer

Configure a VPC endpoint with a bucket policy to restrict access to specific items.

Answer

Store user-specific items in separate S3 buckets and use IAM policies to restrict bucket access.

Question 10

Which THREE of the following are best practices for managing data storage costs in Amazon S3? (Choose 3.)

Accepted Answer

Use S3 Lifecycle policies to transition objects to S3 Glacier Deep Archive after a specified period.. Option A is correct because lifecycle policies transition data to lower-cost storage classes. Option C is correct because S3 Intelligent-Tiering automatically optimizes costs for unknown access patterns. Option E is correct because S3 Object Lock prevents accidental deletion but can be used with lifecycle policies to archive. Option B is wrong because S3 Standard costs more for infrequent access. Option D is wrong because it increases costs.

Answer

Store all data in S3 Standard for maximum durability.

Answer

Create multiple bucket replicas in different regions to ensure availability.

Question 11

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.. Option B is correct because Multi-AZ provides automatic failover. Option D is correct because the standby instance is in a different AZ. Option A is wrong because read replicas are separate from Multi-AZ. Option C is wrong because Multi-AZ does not support cross-region failover. Option E is wrong because Multi-AZ does not automatically scale storage.

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 12

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.. Option A is correct because the policy uses 'dynamodb:LeadingKeys' condition to restrict access to items where the partition key equals the Cognito identity ID (sub). This provides fine-grained access control. Option B is wrong because it allows only GetItem and Query, not Scan. Option C is wrong because it restricts to a specific table. Option D is wrong because it does not allow writes.

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 13

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.. Option B is correct because MFADelete requires multi-factor authentication to permanently delete object versions. Option A is wrong because MFA is not required for all operations, only for version deletion and suspending versioning. Option C is wrong because it's not for all modifications. Option D is wrong because it's not for all 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 14

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.. Option D is correct because the table is defined with Parquet SerDe but the INPUTFORMAT is TextInputFormat, which is incompatible. For Parquet files, the INPUTFORMAT should be 'org.apache.hadoop.hive.ql.io.parquet.MapredParquetInputFormat'. Option A is wrong because the location is valid. Option B is wrong because the table name is valid. Option C is wrong because the SerDe is correct for Parquet, but the mismatch with INPUTFORMAT causes the 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 15

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'. Option C is correct because the condition 's3:x-amz-server-side-encryption': 'aws:kms' enforces SSE-KMS. Option A denies requests with SSE-S3 but allows unencrypted uploads. Option B denies without encryption but allows SSE-S3. Option D denies SSE-KMS, which is the opposite of what is needed.

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