DBS-C01 Practice Test 25 — 15 Questions

Question 1

Which THREE are factors to consider when choosing between Amazon RDS and Amazon DynamoDB? (Select THREE.)

Accepted Answer

Serverless capacity management. Amazon RDS requires manual or auto-scaling of compute and storage capacity, while DynamoDB offers serverless capacity management with on-demand mode that automatically scales throughput based on traffic. This is a key differentiator when deciding between provisioned capacity (RDS) and fully managed, pay-per-request scaling (DynamoDB).

Answer

Encryption at rest requirements

Answer

Need for in-memory caching

Question 2

A company is using Amazon Aurora MySQL-Compatible Edition. The security team wants to restrict access to the database so that only specific applications running on Amazon EC2 instances can connect. The EC2 instances are in the same VPC as the Aurora cluster. Which combination of steps should be taken to enforce this restriction?

Accepted Answer

Configure the Aurora cluster's security group to allow inbound traffic from the EC2 instances' security group.. Configuring the Aurora cluster's security group to allow inbound traffic from the EC2 instances' security group is the correct approach because security groups can reference other security groups as a source, enabling dynamic, instance-level access control without managing individual IP addresses. Option A is incorrect because IAM database authentication manages user authentication at the database level, not network access. Option B is incorrect because the DB subnet group defines the subnets where the Aurora cluster can be placed, not traffic filtering rules. Option C is incorrect because network ACLs are stateless and operate at the subnet boundary, making them less granular and harder to manage for instance-specific access compared to security group references.

Answer

Enable IAM database authentication and create database users for each application.

Answer

Modify the DB subnet group to include only subnets where the EC2 instances reside.

Answer

Use a network ACL to allow traffic only from the EC2 instances' IP addresses.

Question 3

A company uses Amazon DynamoDB for a session management store. The application writes and reads session data frequently. The team notices that write requests occasionally fail with ProvisionedThroughputExceededException. They want a cost-effective solution to handle these bursts. What should they do?

Accepted Answer

Enable DynamoDB Auto Scaling for the table. DynamoDB Auto Scaling dynamically adjusts the provisioned write capacity based on actual traffic patterns, handling bursts cost-effectively by scaling up during spikes and down during lulls. This avoids the fixed-cost overhead of a higher provisioned value (Option A) and directly addresses the ProvisionedThroughputExceededException by ensuring sufficient capacity during bursts.

Answer

Increase the provisioned write capacity to a higher fixed value

Answer

Use DynamoDB Accelerator (DAX) to cache writes

Answer

Implement an Amazon SQS queue to buffer writes

Question 4

A company's Amazon RDS for PostgreSQL instance is experiencing a high number of connections, causing performance degradation. The DBA wants to identify which user and application are creating the most connections. What should the DBA do?

Accepted Answer

Enable Performance Insights and use the 'db.sql_tokenized' dimension to analyze connections by user.. Performance Insights with the 'db.sql_tokenized' dimension allows database administrators to group and analyze database connections by user and application, helping identify the source of high connection counts. Option A (CloudTrail) logs API calls, not database-level logins. Option C (Enhanced Monitoring) provides OS-level metrics like connection count but does not break down by user or application. Option D (VPC Flow Logs) captures network traffic metadata, not database connection details.

Answer

Enable AWS CloudTrail to log database logins.

Answer

Enable Enhanced Monitoring and check the 'Connection Count' metric.

Answer

Enable VPC Flow Logs to track connection attempts.

Question 5

A company uses Amazon DynamoDB to store user session data for a web application. The table has a partition key of 'user_id' and no sort key. Each item is about 5 KB. The application performs frequent GetItem and UpdateItem operations. Recently, the application has been experiencing higher than expected latency and some throttling. The table's read and write capacity are set to on-demand mode. The CloudWatch metrics show that the ConsumedWriteCapacityUnits are well below the provisioned limits (if they were provisioned), but there are occasional ThrottledWriteEvents. The application team also notices that the throttling occurs for specific users. What is the most likely cause and solution?

Accepted Answer

Implement write sharding by appending a random suffix to the partition key for high-traffic users.. The throttling for specific users indicates a hot partition issue. Even in on-demand mode, DynamoDB has a per-partition throughput limit (3,000 RCU and 1,000 WCU per partition). If a single partition key (user_id) receives too much traffic, it can throttle. Write sharding by appending a random suffix to the partition key distributes the writes across multiple partitions, alleviating the hot partition.

Answer

Create a global secondary index with a different partition key for the hot users.

Answer

Add a sort key to the table to improve data distribution.

Answer

Switch to provisioned capacity mode and increase the write capacity units significantly.

Question 6

A company is planning to deploy an Amazon RDS for PostgreSQL instance. Which of the following is a required step to enable automated backups?

Accepted Answer

Set the backup retention period to a value greater than 0.. Automated backups in Amazon RDS for PostgreSQL are enabled by setting a backup retention period greater than 0 days. By default, the retention period is 0, which disables automated backups. Once set to a value between 1 and 35 days, RDS automatically takes daily snapshots and retains transaction logs for point-in-time recovery within that window.

Answer

Set a preferred maintenance window.

Answer

Enable encryption at rest.

Answer

Configure a Multi-AZ deployment.

Question 7

A company is deploying a globally distributed application that requires a low-latency, highly available database with multi-region write support. The application needs to handle conflicts automatically. Which AWS database solution meets these requirements?

Accepted Answer

Amazon DynamoDB global tables. Amazon DynamoDB global tables provide a fully managed, multi-region, multi-active database solution that automatically replicates data across AWS Regions, supports low-latency reads and writes from any region, and uses conflict resolution based on 'last writer wins' (LWW) with a timestamp vector clock. This meets the requirement for a globally distributed application needing automatic conflict handling without custom code.

Answer

Amazon Aurora Global Database

Answer

Amazon ElastiCache for Redis global datastore

Answer

Amazon RDS Multi-AZ with cross-region read replicas

Question 8

A database administrator is troubleshooting a backup failure for an Amazon RDS for SQL Server DB instance. The error message states 'Insufficient storage capacity for backup. Free storage space is 0 GB.' The DB instance has 200 GB allocated storage. What is the most likely cause?

Accepted Answer

The DB instance has insufficient free storage space to perform the backup.. RDS for SQL Server native backups (and automated backups) require free space on the DB instance's EBS volume to stage the backup before it is uploaded to S3. When free storage reaches 0 GB, the backup operation fails with the 'Insufficient storage capacity for backup' error. The fix is to free space (shrink files, remove old data) or increase allocated storage, which RDS can do via storage autoscaling.

Answer

The DB instance has reached the maximum number of manual snapshots.

Answer

The transaction logs are consuming all allocated storage.

Answer

The backup retention period is set to 0 days, disabling automated backups.

Question 9

An e-commerce application stores order data in Amazon RDS for MySQL. The database has grown to 1.5 TB and the company needs to retain data for 7 years for compliance. Current queries are becoming slow due to the large table size. The compliance requirement mandates that data older than 1 year must be retained but is rarely accessed. What strategy would reduce the active table size while maintaining compliance?

Accepted Answer

Partition the table by date and archive partitions older than 1 year to Amazon S3 using AWS DMS.. Partitioning the table by date allows you to efficiently archive older, rarely accessed data to Amazon S3 using AWS DMS, reducing the active table size while retaining data for 7 years as required. This approach maintains compliance by keeping the archived data accessible in S3, and it improves query performance on the active partition by reducing the volume of data scanned.

Answer

Create a read replica and run reports against it.

Answer

Delete data older than 1 year and use automated backups for compliance.

Answer

Vertically partition the table to separate frequently and infrequently accessed columns.

Question 10

A company is using Amazon RDS for PostgreSQL with read replicas to offload read traffic. The company wants to ensure that the read replicas are always in sync with the primary instance. Which metric should the company monitor to detect replication lag?

Accepted Answer

ReplicaLag. ReplicaLag is the CloudWatch metric that Amazon RDS publishes specifically to report how far a read replica has fallen behind its source DB instance, measured in seconds. Monitoring it directly tells the company whether replicas are in sync with the primary, which is exactly the stated requirement.

Answer

DiskQueueDepth

Answer

TransactionLogsDiskUsage

Answer

ReadLatency

Question 11

A company has an Aurora MySQL cluster with three instances. The current writer instance is 'mycluster-instance-1'. The company wants to failover to 'mycluster-instance-2' for maintenance. What is the most direct way to achieve this?

Accepted Answer

Use the AWS CLI: aws rds failover-db-cluster --db-cluster-identifier mycluster --target-db-instance-identifier mycluster-instance-2. The AWS CLI command `aws rds failover-db-cluster` with the `--target-db-instance-identifier` parameter allows you to explicitly specify which Aurora replica should become the new writer instance. This is the most direct and supported method to initiate a controlled failover to 'mycluster-instance-2' without rebooting the current writer or manually modifying endpoints.

Answer

Change the cluster's endpoint to point to instance-2.

Answer

Modify 'mycluster-instance-2' to promote it to writer.

Answer

Reboot 'mycluster-instance-1' to trigger a failover.

Question 12

A company's RDS for SQL Server instance has been running for 3 years. The DBA notices that the DB instance's allocated storage (500 GB) is 80% full. The application is write-heavy. The DBA needs to increase storage without downtime. What is the most efficient way to achieve this?

Accepted Answer

Use the Modify DB Instance API to increase allocated storage.. Amazon RDS supports storage scaling without downtime via the Modify DB Instance API, which increases allocated storage. For SQL Server, storage can be increased but not decreased. This is the most efficient method because it requires no data migration and the instance remains available during the modification.

Answer

Attach an additional EBS volume to the DB instance.

Answer

Create a new DB instance with larger storage and migrate data.

Answer

Take a snapshot and restore a new instance with larger storage.

Question 13

A company is migrating a 500 GB Oracle database to Amazon Aurora PostgreSQL. Which THREE steps should be part of the migration plan?

Accepted Answer

Use AWS DMS to perform a full load and ongoing replication from Oracle to Aurora.. Option C is correct because AWS Database Migration Service (DMS) is the standard tool for heterogeneous migrations, performing a full load of the 500 GB Oracle database and optionally ongoing replication (CDC) to keep Aurora PostgreSQL in sync until cutover. Option D is correct because AWS Schema Conversion Tool (SCT) is required to convert Oracle-specific schema objects, PL/SQL, and data types into PostgreSQL-compatible DDL before DMS can load the data. Option E is correct because a migration plan must include post-migration validation of row counts, data integrity, and application functional testing against Aurora PostgreSQL to confirm the cutover is safe. Option A is not appropriate because Snowball is for bulk physical data transfer, not for logical database migration into Aurora PostgreSQL. Option B is not required because Direct Connect is a network connectivity option and does not itself perform schema conversion or data migration for this scenario.

Answer

Use AWS Snowball to transfer the database files.

Answer

Set up AWS Direct Connect between on-premises and AWS.

Question 14

A company runs a production Amazon RDS for PostgreSQL Multi-AZ DB instance (db.r5.large) with 500 GB of General Purpose SSD (gp2) storage. The application experiences intermittent latency spikes every 15 minutes. Monitoring shows that during these spikes, the ReadIOPS metric on the primary instance spikes to 5,000 IOPS (the baseline is 1,500 IOPS), and the BurstBalance drops from 100% to 20% then recovers. There is no increase in CPU or connections. The application uses connection pooling with pgBouncer on an EC2 instance. The team has verified that no long-running queries or index scans are causing the spikes. Which action is MOST likely to resolve the intermittent latency?

Accepted Answer

Migrate the storage to gp3 with a baseline of 3,000 IOPS and 125 MB/s throughput.. The latency spikes are caused by gp2 storage burst credit exhaustion. The 500 GB gp2 volume has a baseline of 1,500 IOPS, but the workload spikes to 5,000 IOPS every 15 minutes, rapidly consuming burst credits. Migrating to gp3 provides a baseline of 3,000 IOPS and 125 MB/s throughput without relying on burst credits, thus eliminating the credit exhaustion issue. Option A (read replica) does not resolve the primary instance's write IOPS spikes. Option B (larger instance) does not address storage IOPS limitations; CPU and connections are already normal. Option D (scale storage to 1,000 GB) would increase the gp2 baseline to 3,000 IOPS and provide more burst credits, but gp3 offers a simpler, more cost-effective solution with consistent performance and no credit-based throttling.

Answer

Create a read replica and redirect read traffic to it.

Answer

Increase the DB instance to db.r5.xlarge to improve CPU and network performance.

Answer

Scale the storage to 1,000 GB to increase baseline IOPS and burst credits.

Question 15

A company is deploying a new multi-AZ Amazon RDS for PostgreSQL database. The security team requires that all traffic to the database be encrypted in transit. Which configuration ensures this?

Accepted Answer

Enable SSL/TLS and require client connections to use SSL. Enabling SSL/TLS on the RDS instance and requiring client connections to use SSL ensures that all data transmitted between clients and the database is encrypted in transit. This is achieved by setting the rds.force_ssl parameter to 1 in the DB parameter group, which enforces SSL/TLS for all connections, meeting the security team's requirement for encryption in transit.

Answer

Use a customer master key (CMK) for RDS

Answer

Place the RDS instance in a public subnet

Answer

Enable encryption at rest using AWS KMS