DBS-C01 Mock Exam 86 — 25 Questions

Question 1

A company uses an Amazon RDS for PostgreSQL database with Multi-AZ deployment. The security team wants to audit all SQL queries executed against the database for compliance purposes. Which solution should be implemented to capture and store the queries?

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

Accepted Answer

Enable PostgreSQL query logging and publish logs to Amazon CloudWatch Logs.. Enabling PostgreSQL query logging and publishing those logs to CloudWatch Logs captures all SQL queries for auditing. Option A is wrong because CloudTrail captures API calls, not SQL queries. Option B is wrong because Performance Insights captures performance metrics, not the text of SQL queries. Option C is wrong because RDS event notifications are for database events (e.g., failover, scaling), not for capturing SQL query text.

Answer

Use AWS CloudTrail to capture SQL queries.

Answer

Enable Performance Insights and store the data in CloudWatch Logs.

Answer

Enable RDS event notifications for database queries.

Question 2

A company is designing a database for an IoT application that ingests millions of small sensor readings per second. The data is append-only and queries are primarily time-based aggregations with low latency requirements (under 10 ms). Which AWS database service is most suitable for this workload?

Accepted Answer

Amazon Timestream. Amazon Timestream is a purpose-built time-series database designed for IoT and operational applications that ingest high volumes of append-only data. It automatically manages storage tiers (in-memory and magnetic) and provides built-in time-based aggregation functions, enabling queries with sub-10 ms latency for recent data. This makes it the most suitable choice for the described workload of millions of sensor readings per second with low-latency aggregation queries.

Answer

Amazon DynamoDB

Answer

Amazon ElastiCache

Answer

Amazon Aurora

Question 3

Which TWO AWS services can be used to implement a serverless database architecture for variable workloads?

Accepted Answer

Amazon Aurora Serverless v2. Amazon Aurora Serverless v2 is correct because it automatically scales database capacity up or down based on application demand, providing a serverless architecture for variable workloads without the need to manage database instances. Amazon DynamoDB is correct because it is a fully managed NoSQL serverless database that automatically scales throughput and storage to handle variable workloads, requiring no server provisioning or management.

Answer

Amazon Redshift

Answer

Amazon RDS Proxy

Answer

Amazon ElastiCache

Question 4

A company wants to migrate an on-premises MySQL database to Amazon RDS for MySQL. The database is 500 GB and experiences heavy write traffic. They need to minimize downtime and ensure no data loss. Which approach should they take?

Accepted Answer

Set up MySQL replication from the on-premises database to RDS, then promote the RDS instance when ready.. Setting up native MySQL replication from the on-premises database to Amazon RDS for MySQL allows continuous synchronization with minimal downtime. When ready, you simply stop replication and promote the RDS instance, ensuring zero data loss since all transactions are replicated in near real-time.

Answer

Use AWS DMS with a full load task, then cut over the application to RDS.

Answer

Create an RDS read replica of the on-premises database, then promote it to a standalone instance.

Answer

Use mysqldump to export the database and mysql command to import into RDS during a maintenance window.

Question 5

A developer accidentally deleted an RDS database. Which action will allow the database to be restored with the least data loss?

Accepted Answer

Restore from the latest automated backup using point-in-time recovery.. Point-in-time recovery (PITR) allows you to restore an RDS DB instance to any second within the automated backup retention period, typically up to the last five minutes. This minimizes data loss because it replays transaction logs from the latest automated backup to the specified time, recovering changes made right up to the deletion moment. Automated backups are enabled by default with a 7-day retention, making PITR the most granular recovery option.

Answer

Use the 'Recycle Bin' feature to recover the RDS instance.

Answer

Restore from the latest manual snapshot.

Answer

Create a new RDS instance and hope for the best.

Question 6

A company's Amazon RDS for PostgreSQL instance is running out of storage. The DB instance has auto-scaling enabled, but the storage did not increase. What is the most likely cause?

Accepted Answer

The DB instance has exceeded the Maximum Storage Duration setting.. Amazon RDS storage auto-scaling will not increase storage beyond the maximum storage threshold set by the user. If the instance has reached this maximum threshold, auto-scaling stops, even if free space is low. The phrase 'Maximum Storage Duration' in the option refers to this threshold. Option D is incorrect because the condition for auto-scaling is based on free space being below 10%, not on whether the maximum storage has been reached. If the maximum threshold has not been reached, auto-scaling should occur when free space is low.

Answer

The DB instance class does not support storage auto-scaling.

Answer

The DB instance is smaller than the minimum storage size for auto-scaling.

Answer

The storage usage has not reached the maximum allocated storage.

Question 7

A company is running a production Amazon RDS for MySQL Multi-AZ DB instance. The database experiences intermittent high latency and the CloudWatch 'ReadLatency' metric spikes during periods of heavy read traffic. The application uses a single database endpoint. What is the MOST effective way to reduce read latency without changing the application code?

Accepted Answer

Enable a Multi-AZ deployment with one or more readable standby replicas.. Enabling a Multi-AZ deployment with one or more readable standby replicas allows you to offload read traffic to the standby instances using the Read Replica endpoint, reducing load on the primary and lowering ReadLatency. Since the application uses a single database endpoint, you can use Amazon RDS's built-in reader endpoint (for a Multi-AZ DB cluster) or configure a custom DNS to distribute reads, without modifying application code. This directly addresses the intermittent high latency during heavy read traffic by scaling read capacity horizontally.

Answer

Implement database sharding across multiple RDS instances.

Answer

Enable Multi-AZ on the existing DB instance to provide a standby for failover.

Answer

Increase the DB instance class to a larger size.

Question 8

A company is deploying a new application on AWS that requires a highly available relational database with automatic failover and read scaling. The database size is 100 GB and the workload is balanced between reads and writes. Which THREE AWS services or features should be used?

Accepted Answer

Multi-AZ deployment. Multi-AZ deployment (Option A) is correct because it provides automatic failover for Amazon RDS by provisioning a synchronous standby replica in a different Availability Zone. If the primary DB instance fails, Amazon RDS automatically fails over to the standby, ensuring high availability without manual intervention. This directly meets the requirement for automatic failover in a relational database scenario.

Answer

DynamoDB Accelerator (DAX)

Answer

Amazon RDS Proxy

Question 9

A company is running a MySQL database on Amazon RDS for a web application. The application experiences read-heavy traffic, and the company wants to improve read performance without changing the application code. Which design should the database specialist recommend?

Accepted Answer

Create one or more read replicas of the RDS DB instance.. Amazon RDS read replicas allow you to offload read traffic from the primary DB instance without any application code changes. The application simply connects to the read replica endpoint(s) for SELECT queries, while writes continue to the primary instance. This directly addresses the read-heavy workload by distributing read requests across multiple copies of the database.

Answer

Implement an Amazon ElastiCache Redis cluster in front of the database.

Answer

Increase the instance size of the RDS DB instance.

Answer

Enable DynamoDB Accelerator (DAX) for the RDS instance.

Question 10

Refer to the exhibit. A database administrator runs the AWS CLI command and gets the following output: {"Engine":"mysql","DBInstanceStatus":"available","MultiAZ":true,"SecondaryAvailabilityZone":"us-east-1b"}. What can be concluded about the database deployment?

Accepted Answer

The database is a Multi-AZ deployment with a standby in a different Availability Zone.. The output shows `"MultiAZ":true` and `"SecondaryAvailabilityZone":"us-east-1b"`, which are explicit indicators of a Multi-AZ deployment for an RDS MySQL instance. In a Multi-AZ deployment, Amazon RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone, and the `SecondaryAvailabilityZone` field confirms the standby's location. This matches option D exactly.

Answer

The database is a Single-AZ deployment.

Answer

The database has a Read Replica in a different Availability Zone.

Answer

The database is an Amazon Aurora cluster.

Question 11

A company has an Amazon RDS for SQL Server Multi-AZ DB instance with a standby replica in a different AWS Region. The database is encrypted with a KMS key. The company needs to implement automated backups that are also encrypted and stored in a cross-region S3 bucket. The backups must be retained for 3 years. Which solution meets these requirements with the LEAST administrative effort?

Accepted Answer

Configure RDS to send automated backups directly to the cross-region S3 bucket using the AWS Backup service.. AWS Backup can be used to manage automated backups of RDS instances and store them in a cross-region S3 bucket. AWS Backup natively supports RDS and allows you to create backup plans that automatically take snapshots and copy them to a different region, storing them in S3. The backups are encrypted using the KMS key, and you can set retention policies for 3 years. This solution requires minimal administrative effort as AWS Backup automates the entire process. Option B is incorrect because RDS cross-Region backup copy stores backups in the destination region's RDS-managed storage, not in an S3 bucket as required. Option C is incorrect because AWS DMS is designed for migrations, not for ongoing backup management. Option D is incorrect because manual snapshots require manual intervention and do not provide automated backups.

Answer

Enable automated backups on the RDS instance, configure cross-Region backup copy to a destination Region, and store the backups in an S3 bucket with S3 Object Lock enabled for retention.

Answer

Use AWS Database Migration Service (DMS) to continuously replicate the database to an S3 bucket in the target region.

Answer

Create manual snapshots of the RDS instance, copy them to the cross-region S3 bucket using AWS CLI, and set a lifecycle policy for retention.

Question 12

Which TWO actions should a company take to secure an Amazon RDS for MySQL database that is accessible from the internet? (Choose two.)

Accepted Answer

Use a security group that restricts inbound traffic to only the required IP addresses.. Options A and E are correct. Option A: Using a security group to restrict inbound traffic to only required IP addresses limits exposure to the internet. Option E: Placing the DB instance in a private subnet without a public IP address ensures it is not directly accessible from the internet. Option B is incorrect because disabling encryption at rest reduces security and does not address internet accessibility. Option C is incorrect because using the default VPC with a public subnet and a network ACL that allows all traffic increases exposure. Option D is incorrect because launching the DB instance in a public subnet with a public IP address makes it directly reachable from the internet.

Answer

Disable encryption at rest to reduce latency.

Answer

Use the default VPC with a public subnet and a network ACL that allows all traffic.

Answer

Launch the DB instance in a public subnet with a public IP address.

Question 13

A company is deploying a new web application that uses Amazon RDS for MySQL. The application has unpredictable read traffic spikes. The company wants to minimize read latency and automatically scale read capacity. What is the MOST cost-effective solution?

Accepted Answer

Create an Amazon RDS read replica and configure the application to use it for read traffic. Amazon RDS read replicas allow you to offload read traffic from the primary DB instance to one or more replicas, which can be scaled horizontally by adding more replicas as needed. This is the most cost-effective solution among the options for handling unpredictable read spikes because it directly addresses read capacity scaling without the cost of a full caching layer. Multi-AZ provides only high availability, not read scaling; ElastiCache adds cost and complexity; RDS Proxy manages connections but does not scale read capacity.

Answer

Use Amazon ElastiCache as a caching layer

Answer

Use Amazon RDS Proxy to manage connections

Answer

Deploy the RDS instance in a Multi-AZ configuration

Question 14

Refer to the exhibit. A developer deploys this CloudFormation template. An application on the EC2 instance cannot connect to the RDS MySQL database. What is the MOST likely cause?

Accepted Answer

The EC2 security group allows inbound MySQL from 0.0.0.0/0 but the RDS security group only allows traffic from the VPC CIDR, which does not include the EC2 security group.. The RDS security group only allows inbound MySQL traffic from the VPC CIDR (e.g., 10.0.0.0/16), but the EC2 instance's security group is not referenced. Since the EC2 instance's private IP may fall outside that CIDR (e.g., if it uses a different subnet or a public IP), the RDS security group blocks the connection. Security group rules must explicitly reference the EC2 security group ID to allow traffic from that specific instance, not just the VPC CIDR.

Answer

The RDS instance has encryption enabled, preventing access from EC2.

Answer

The RDS instance has DeletionProtection enabled, which blocks connections.

Answer

The EC2 instance is in a different Availability Zone than the RDS instance.

Question 15

A social media analytics company uses Amazon DynamoDB as the primary data store for user session data. Each session record has a partition key of user_id (String) and a sort key of session_start_time (Number, epoch). The application often queries the most recent 10 sessions for a given user. The traffic pattern shows that 90% of reads are for the last 10 sessions, while 10% are for historical sessions. The table has a provisioned read capacity of 5000 RCU and consistently experiences throttled read requests during peak hours. The company wants to optimize read performance without changing the provisioned capacity. Which design change will MOST improve read performance for this workload?

Accepted Answer

Create a Global Secondary Index (GSI) with the same partition key and a sort key of session_start_time, but query with ScanIndexForward=false and Limit=10.. Creating a GSI with the same partition key (user_id) and sort key (session_start_time) allows you to query with ScanIndexForward=false and Limit=10 to efficiently retrieve only the most recent 10 sessions per user. This avoids scanning all sessions for a user, reducing consumed read capacity and eliminating throttling without increasing provisioned RCU. The GSI also supports the 90% workload pattern by providing a targeted index that minimizes read unit consumption.

Answer

Increase the provisioned read capacity to 10000 RCU to handle the peak load.

Answer

Enable DynamoDB Accelerator (DAX) with default settings to cache the most recent sessions.

Answer

Configure Amazon ElastiCache for Redis as a read-through cache for session data.

Question 16

A company wants to centrally manage database user credentials and rotate them automatically. The database is an Amazon RDS for MySQL instance. Which AWS service should be used?

Accepted Answer

AWS Secrets Manager. AWS Secrets Manager (option A) is the correct service because it is designed to centrally manage database credentials and can automatically rotate them for Amazon RDS for MySQL instances on a schedule you define. Option B (AWS CloudHSM) provides hardware security modules for cryptographic key storage, not credential management or rotation. Option C (IAM) is used for controlling access to AWS resources and supports IAM database authentication for RDS, but it does not manage database user passwords or provide automatic rotation of those passwords. Option D (AWS Systems Manager Parameter Store) can store secrets securely, but it does not offer native automatic rotation of RDS database credentials; that functionality requires Secrets Manager.

Answer

AWS CloudHSM

Answer

AWS Identity and Access Management (IAM)

Answer

AWS Systems Manager Parameter Store

Question 17

A company has an Amazon DynamoDB table with on-demand capacity mode. The table is used by a serverless application. The company wants to receive an alert when the read request rate exceeds a certain threshold. Which CloudWatch metric and alarm should be used?

Accepted Answer

Alarm on the 'ConsumedReadCapacityUnits' metric.. The 'ConsumedReadCapacityUnits' metric reflects the actual number of read capacity units consumed by the table. By setting an alarm on this metric, you can trigger an alert when the read request rate exceeds a defined threshold, which is appropriate for an on-demand table where capacity scales automatically but you still want to monitor usage.

Answer

Alarm on the 'ReadThrottleEvents' metric.

Answer

Alarm on the 'ProvisionedReadCapacityUnits' metric.

Answer

Alarm on the 'SuccessfulRequestLatency' metric.

Question 18

A developer runs the command `aws rds describe-db-instances --db-instance-identifier mydb` and gets the output containing `Source_Region: us-east-1` and `Replica_Mode: async`. Which conclusion can be drawn about the database configuration?

Accepted Answer

The database is a read replica of another instance. The output from the describe-db-instances command indicates that this database is configured as a read replica. Read replicas in Amazon RDS are identified by the presence of a source region and asynchronous replication mode, which are characteristic of read replica configurations. Multi-AZ deployments use synchronous replication and do not expose these fields, making option D the only viable conclusion.

Answer

The database is a Multi-AZ read replica

Answer

The database engine is Aurora MySQL

Answer

The database is a primary instance in a Multi-AZ deployment

Question 19

A media company stores video metadata in Amazon DynamoDB. Each record has a partition key of video_id and a sort key of uploaded_timestamp. The application frequently queries videos by genre and upload date. The access pattern is read-heavy with occasional writes. The table is provisioned with 3000 RCUs and 1000 WCUs. The company notices that queries by genre are slow and consume many RCUs. Which design change should be made to optimize for this workload?

Accepted Answer

Create a global secondary index (GSI) with genre as partition key and uploaded_timestamp as sort key.. Creating a Global Secondary Index (GSI) with genre as the partition key and uploaded_timestamp as the sort key allows efficient querying by genre and date without scanning the entire table. This directly supports the access pattern, reducing RCU consumption by using index key lookups instead of full table scans. The GSI is ideal for read-heavy workloads with occasional writes, as it offloads query traffic from the main table.

Answer

Use DynamoDB Accelerator (DAX) to cache query results.

Answer

Create a local secondary index (LSI) with genre as sort key and uploaded_timestamp as partition key.

Answer

Increase the provisioned RCUs to 6000.

Question 20

A company runs a critical Amazon RDS for PostgreSQL database. They notice that the 'DiskQueueDepth' metric is consistently high and the 'FreeStorageSpace' is below 10%. The database is used for OLTP workloads. What is the MOST immediate action to take?

Accepted Answer

Modify the DB instance to increase allocated storage.. Increasing allocated storage quickly addresses the low free storage space (below 10%) and high DiskQueueDepth, which indicates I/O bottlenecks due to insufficient storage. Option A is wrong because upgrading to a larger instance class improves memory and CPU but does not directly resolve storage shortage or I/O throttling caused by low disk space. Option C is wrong because switching to Provisioned IOPS improves latency and throughput but does not increase storage capacity. Option D is wrong because creating a read replica offloads read traffic but does not increase storage on the primary instance.

Answer

Upgrade to a larger DB instance class.

Answer

Switch the instance to Provisioned IOPS storage.

Answer

Create a read replica to offload read traffic.