DBS-C01 Practice Test 27 — 15 Questions

Question 1

A financial services company uses Amazon DynamoDB to store transaction records. The table has a partition key of 'AccountId' and a sort key of 'TransactionDate'. The company needs to run analytical queries that aggregate transactions by account and month. Currently, queries are slow due to full table scans. Which design change will improve query performance most effectively?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Create a Global Secondary Index (GSI) with partition key AccountId and sort key Month.. Creating a Global Secondary Index (GSI) with partition key AccountId and sort key Month allows the analytical queries to efficiently retrieve aggregated data by account and month without scanning the entire base table. The GSI reorganizes data by month, enabling DynamoDB to use the sort key for range queries and avoid full table scans, which directly addresses the performance issue.

Answer

Add DynamoDB Accelerator (DAX) to the table.

Answer

Change the table's sort key from TransactionDate to Month.

Answer

Enable DynamoDB Streams and process the stream with AWS Lambda to pre-aggregate results.

Question 2

A company is migrating an on-premises MySQL database to Amazon RDS for MySQL. The database is 2 TB in size and the network bandwidth is 100 Mbps. The company needs to minimize downtime. Which migration strategy should be used?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication.. AWS DMS with ongoing replication is the correct strategy because it allows you to perform a full load of the 2 TB database while simultaneously capturing ongoing changes from the source MySQL binlog. This minimizes downtime by enabling a cutover with only a brief pause to ensure replication lag is zero, rather than requiring a long period of application downtime for a full export and import.

Answer

Copy database files to Amazon S3, then restore to RDS using native restore.

Answer

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

Answer

Use AWS Server Migration Service to migrate the database server.

Question 3

A company wants to deploy a DynamoDB table that requires consistent single-digit millisecond latency regardless of traffic spikes. Which DynamoDB capacity mode should be selected?

Accepted Answer

On-demand capacity mode.. On-demand capacity mode is the correct choice because it automatically scales read and write capacity up and down based on actual traffic, eliminating the need for capacity planning and ensuring consistent single-digit millisecond latency even during unpredictable traffic spikes. This mode is designed for workloads with variable or bursty traffic patterns where latency sensitivity is critical.

Answer

DynamoDB Accelerator (DAX) enabled.

Answer

Provisioned capacity mode with auto scaling.

Answer

Provisioned capacity mode with fixed read/write capacity.

Question 4

Which TWO design patterns are commonly used to handle hot partitions in Amazon DynamoDB? (Choose 2.)

Accepted Answer

Write sharding. Write sharding distributes writes across multiple partition keys to prevent a single partition from exceeding the 1,000 WCU limit. Adding random suffixes to partition keys is a specific write sharding technique that spreads writes across many partitions, avoiding hot spots.

Answer

Decreasing write capacity units

Answer

Using a single partition key

Answer

Increasing read capacity units

Question 5

A company has a multi-player game that uses DynamoDB to store game state. The access pattern is write-heavy, and the game state for each active game session is updated frequently. The team notices throttling on the table during peak hours. The table has a partition key of game_id and no sort key. What design change would best reduce throttling?

Accepted Answer

Use a composite key with a random suffix on the partition key.. The write-heavy access pattern with frequent updates to the same game sessions causes throttling because all writes for a given game_id hit the same partition, creating a hot partition. Using a composite key with a random suffix on the partition key distributes the writes across multiple partitions, reducing the per-partition write throughput and alleviating throttling.

Answer

Enable DynamoDB global tables.

Answer

Enable DynamoDB Accelerator (DAX) for the table.

Answer

Increase the provisioned read capacity units (RCU).

Question 6

A database administrator is troubleshooting a performance issue on an Amazon RDS for SQL Server instance. The CPU utilization is consistently above 90%, and the number of database connections is high. Which Amazon CloudWatch metric should be analyzed first to determine if the issue is due to a specific query?

Accepted Answer

Enhanced Monitoring (cpuUtilization per process). Enhanced Monitoring provides per-process CPU utilization metrics, which allow you to identify if a specific SQL Server query or session is consuming excessive CPU. Unlike aggregate metrics like CPUUtilization, Enhanced Monitoring breaks down CPU usage by process (e.g., sqlservr.exe), enabling you to pinpoint a problematic query. This is the most direct way to determine if the high CPU is driven by a specific query rather than general load.

Answer

DatabaseConnections

Answer

ReadIOPS

Answer

CPUUtilization

Question 7

Which TWO design patterns help meet ACID compliance requirements in a distributed database environment while maintaining high availability?

Accepted Answer

Implement Amazon Aurora Global Database for cross-Region ACID transactions.. Amazon Aurora Global Database is designed to support cross-Region ACID transactions by using a primary cluster in one AWS Region and up to five secondary read-only clusters in other Regions. It replicates data asynchronously from the primary to the secondary Regions, but each secondary cluster can be promoted to a primary in under a minute, ensuring high availability while maintaining ACID compliance for transactions that span multiple Regions.

Answer

Use an eventually consistent read model to improve performance.

Answer

Adopt a saga pattern to manage distributed transactions.

Answer

Implement DynamoDB Streams to capture changes for audit.

Question 8

An e-commerce application uses Amazon Aurora MySQL with a Multi-AZ DB cluster. During a recent load test, the application experienced increased read latency. The database cluster consists of one writer and two reader instances. Which THREE actions should be taken to improve read performance?

Accepted Answer

Add more reader instances to the cluster.. Adding more reader instances (Option C) directly reduces the read load per instance, improving read performance. Enabling Aurora Auto Scaling (Option D) automatically adjusts the number of reader instances based on demand, ensuring optimal performance. Implementing Amazon ElastiCache (Option E) caches frequent queries at the application layer, reducing the number of read requests hitting the database. Option A (configuring cross-Region read replicas) introduces network latency and is primarily used for global scaling or disaster recovery, not for reducing latency in a single-region application. Option B (increasing the writer instance class) improves write performance but does not directly affect read latency.

Answer

Configure cross-Region read replicas.

Answer

Increase the instance class of the writer instance.

Question 9

A company is migrating an on-premises Oracle OLTP workload to AWS. The database has complex stored procedures and requires minimal code changes. Which AWS database service is the most suitable target?

Accepted Answer

Amazon RDS for Oracle. Amazon RDS for Oracle is the most suitable target because it provides native Oracle compatibility, allowing the existing complex stored procedures and PL/SQL code to run with minimal or no changes. This minimizes migration risk and effort, which is the primary requirement for an OLTP workload with complex stored procedures.

Answer

Amazon Redshift

Answer

Amazon DynamoDB

Answer

Amazon Aurora PostgreSQL

Question 10

A company has an Amazon DynamoDB table with on-demand capacity. Users report that write requests are occasionally throttled during peak hours. The application uses the AWS SDK and retries with exponential backoff. Which monitoring approach should be used to identify the cause of throttling?

Accepted Answer

Monitor CloudWatch metrics for ThrottledRequests and ConsumedWriteCapacityUnits.. CloudWatch metrics such as ThrottledRequests and ConsumedWriteCapacityUnits directly indicate throttling events and capacity usage, enabling identification of throttling causes even with on-demand capacity. Option A is incorrect because AWS CloudTrail logs API calls but does not provide detailed throttling metrics at the item level. Option B is incorrect because VPC Flow Logs capture network traffic, not database-level throttling. Option D is incorrect because DynamoDB Streams capture item-level changes, not throttling events.

Answer

Use AWS CloudTrail to monitor PutItem API calls for throttling errors.

Answer

Analyze VPC Flow Logs to check for network congestion.

Answer

Enable DynamoDB Streams and process records to monitor throttled requests.

Question 11

A startup is building a multi-tenant SaaS application where each tenant's data must be isolated. The data model is relational with complex joins. Which database deployment model is most appropriate?

Accepted Answer

Provision a separate Amazon RDS instance for each tenant. A multi-tenant SaaS application requiring strict data isolation with complex relational joins demands separate databases per tenant. Amazon RDS provides full relational capabilities (ACID transactions, complex joins) and provisioning separate RDS instances ensures complete tenant isolation, preventing cross-tenant data leakage and allowing independent backup, scaling, and performance tuning for each tenant.

Answer

Use a single Amazon DynamoDB table with a tenant_id partition key

Answer

Use a single Amazon Redshift cluster with tenant_id distribution key

Answer

Use a single Amazon RDS database with a tenant_id column on every table

Question 12

A company has an Amazon DynamoDB table with a global secondary index (GSI). The security team wants to ensure that only certain attributes are returned in query results based on the IAM policy of the calling user. What is the most secure and scalable approach?

Accepted Answer

Use IAM condition keys with 'dynamodb:Attributes' to restrict access to specific attributes.. Using IAM condition keys with 'dynamodb:Attributes' allows fine-grained access control at the attribute level. This is the recommended way to restrict access to specific attributes. Option A is incorrect because using a Lambda middleware adds latency and complexity, and it is not the most secure or scalable approach compared to native IAM attribute-level conditions. Option B is incorrect because creating multiple GSIs for attribute access would be costly and not scalable, and GSIs are not designed for attribute-level access control; they are for querying. Option D is incorrect because VPC endpoints do not control attribute access; they provide network-level security. A bucket policy is for S3, not DynamoDB.

Answer

Use an AWS Lambda function as a middleware to filter attributes before returning results.

Answer

Create multiple global secondary indexes that include only the allowed attributes for each user group.

Answer

Create a VPC endpoint for DynamoDB and attach a bucket policy that limits attribute access.

Question 13

A company uses Amazon RDS for PostgreSQL with Multi-AZ deployment. They experience increased write latency during peak hours. The DB instance size is db.r5.large. Which action would MOST effectively reduce write latency?

Accepted Answer

Disable the Multi-AZ feature and use asynchronous replication with a read replica for failover.. Multi-AZ deployments maintain a synchronous standby replica, which adds write latency because the primary must wait for the standby to acknowledge writes. Disabling Multi-AZ and using asynchronous replication to a read replica eliminates this synchronous overhead, allowing writes to complete faster. Option A increases instance size but doesn't address synchronous replication overhead; option C (synchronous_commit off) risks data loss and is not recommended; option D adds another standby, increasing overhead.

Answer

Switch to a db.r5.xlarge instance type.

Answer

Enable the synchronous_commit parameter to 'off'.

Answer

Enable Multi-AZ with two standby replicas.

Question 14

A company is deploying a new application that uses Amazon RDS for MySQL. The database must be highly available with automatic failover. Which deployment configuration meets these requirements?

Accepted Answer

Multi-AZ deployment with a standby replica in a different Availability Zone. A Multi-AZ deployment for Amazon RDS for MySQL automatically provisions and maintains a synchronous standby replica in a different Availability Zone. In the event of a failure, Amazon RDS automatically fails over to the standby, providing high availability without manual intervention. This configuration meets the requirement for automatic failover and high availability within a single AWS region.

Answer

Single-AZ with a Read Replica in the same region

Answer

Multi-AZ deployment with synchronous replication to a cross-region replica

Answer

Single-AZ with automated backups

Question 15

Which THREE factors should be considered when selecting the backup strategy for an Amazon RDS for PostgreSQL DB instance? (Choose 3.)

Accepted Answer

The backup retention period. The backup retention period directly determines how far back you can perform a point-in-time recovery (PITR) for an RDS for PostgreSQL instance. Amazon RDS stores automated backups and transaction logs for the specified retention period (1 to 35 days), and this period must be aligned with your compliance and operational requirements. Choosing an appropriate retention period is a fundamental factor in defining the backup strategy.

Answer

The need for Multi-AZ deployment

Answer

The encryption at rest requirement