DBS-C01 Practice Exam 67 — 20 Questions

Question 1

A healthcare company is designing a new patient-record system on AWS. The system must store semi-structured clinical notes with nested fields, support complex queries that join patient data with provider information, and provide strong consistency for read-after-write operations. The development team wants to minimize operational overhead for database administration. Which AWS database solution best meets these requirements?

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

Accepted Answer

Amazon Aurora PostgreSQL with Aurora Serverless v2. The requirements include semi-structured data with nested fields, complex joins between patient and provider data, strong consistency, and minimal operational overhead. Aurora PostgreSQL supports JSONB for semi-structured data, full SQL join capabilities, and strong consistency, while Aurora Serverless v2 reduces administrative burden through automatic scaling and managed infrastructure. Other options lack either join support or durability for this workload.

Answer

Amazon ElastiCache for Redis with a cluster mode enabled

Answer

Amazon Neptune with a property graph model

Answer

Amazon DynamoDB with a global secondary index on provider ID

Question 2

A database specialist is investigating why an Amazon RDS for SQL Server DB instance is experiencing slow query performance. The specialist notices that the CPU utilization is high and there are many PAGEIOLATCH_SH waits. Which action should the specialist take to improve performance?

Accepted Answer

Scale up the DB instance class to one with more memory and higher IOPS.. PAGEIOLATCH_SH waits indicate that SQL Server is waiting for data pages to be read from disk into memory. This is typically caused by insufficient memory or slow disk I/O. Scaling up the DB instance to a class with more memory and higher IOPS can reduce these waits by allowing more data to be cached in memory and improving disk read speeds. This directly addresses the root cause of the performance issue.

Answer

Increase the allocated storage size for the DB instance.

Answer

Modify the DB parameter group to increase the max degree of parallelism (MAXDOP).

Answer

Enable Multi-AZ for the DB instance to offload read traffic.

Question 3

A database specialist is troubleshooting an Amazon Aurora PostgreSQL cluster. The application experiences occasional connection timeouts during peak hours. The specialist checks Amazon CloudWatch metrics and sees that 'DatabaseConnections' is high but within the cluster's maximum. They also notice that 'LoginFailures' is zero. Which of the following is the most likely cause of the timeouts?

Accepted Answer

The application's connection pool is not configured correctly, causing connection storms.. The combination of high DatabaseConnections and zero LoginFailures points to connection management issues rather than authentication or network problems. A misconfigured connection pool can cause a surge in connection attempts, leading to timeouts when the database cannot handle the rapid churn. Optimizing the pool settings, such as reducing max connections or increasing idle timeout, can alleviate the issue.

Answer

The security group for the Aurora cluster is blocking connections intermittently.

Answer

The Aurora cluster's reader endpoint is not being used, causing all read traffic to hit the writer.

Answer

The Aurora cluster's writer instance is overloaded due to high CPU utilization.

Question 4

A genomics research team stores variant call data in Amazon Aurora MySQL. Queries frequently join a large variants table against a samples table and filter on genomic coordinates. The team observes that the optimizer sometimes chooses a full table scan on the variants table instead of using the available index. They want to diagnose why the optimizer makes this choice without modifying production data. Which approach should they use?

Accepted Answer

Use EXPLAIN with the optimizer trace feature enabled to inspect the cost calculations and considered plans.. Aurora MySQL exposes the optimizer trace, which records the cost-based reasoning behind plan selection, including indexes evaluated and their estimated costs. Enabling this trace and running EXPLAIN gives the team a read-only view into why the variants table scan was preferred. This is the appropriate diagnostic step before considering remediation such as statistics refresh or index hints.

Answer

Add a FORCE INDEX hint to the query and compare execution times with and without the hint.

Answer

Enable the slow query log and review queries that exceed long_query_time.

Answer

Run ANALYZE TABLE on the variants table to refresh statistics, then re-run the query.

Question 5

A company is deploying a new Amazon RDS for PostgreSQL database that will store sensitive customer data. The security team requires encryption at rest and in transit, and wants to minimize operational overhead for key management. Which TWO configurations should a database specialist implement to meet these requirements? (Choose two.)

Accepted Answer

Enforce SSL/TLS connections by setting the rds.force_ssl parameter to 1 in the parameter group.. Encryption at rest is achieved by enabling RDS storage encryption with an AWS KMS key, which AWS manages with minimal overhead. Encryption in transit is enforced by setting the rds.force_ssl parameter to 1, which requires all client connections to use SSL/TLS. Together, these configurations satisfy the security requirements without adding operational burden.

Answer

Use AWS Secrets Manager to store database credentials and rotate them automatically.

Answer

Enable Transparent Data Encryption (TDE) at the database level using the PostgreSQL pgcrypto extension.

Answer

Configure AWS Certificate Manager (ACM) to issue a private certificate for the RDS instance.

Question 6

A database specialist is managing an Amazon Aurora MySQL cluster. The cluster has one writer and two readers. During a heavy reporting workload, the specialist notices that read replicas are falling behind the writer, causing stale reads. The specialist wants to monitor replication lag and receive an alert when lag exceeds 30 seconds. Which CloudWatch metric should be used?

Accepted Answer

AuroraReplicaLag. The AuroraReplicaLag metric specifically measures the time a replica lags behind the writer in milliseconds. It is available for Aurora MySQL and Aurora PostgreSQL. By creating a CloudWatch alarm on this metric with a threshold of 30000 ms, the specialist can be notified when replication lag exceeds 30 seconds, allowing prompt action to address the reporting workload's impact on read freshness.

Answer

BinLogDiskUsage

Answer

DiskQueueDepth

Answer

ReplicaLag

Question 7

A company runs an Amazon RDS for PostgreSQL DB instance with a 1 TB General Purpose SSD (gp2) volume. The database specialist notices that the storage throughput is insufficient during peak hours, causing elevated latency. The specialist wants to increase the storage throughput without increasing the storage size. What should the specialist do?

Accepted Answer

Modify the DB instance to use a Provisioned IOPS SSD (io1) volume with the desired IOPS.. gp2 storage performance is tied to volume size, so to increase throughput without increasing size, the specialist must switch to a volume type that allows independent IOPS provisioning, such as io1. This directly addresses the need for higher throughput during peak hours.

Answer

Modify the DB instance to increase the allocated storage, which will increase the gp2 baseline IOPS.

Answer

Create a read replica and direct read traffic to it to reduce load on the primary.

Answer

Enable RDS Performance Insights to identify the bottleneck and then increase the instance class.

Question 8

A solutions architect is deploying a new Amazon Aurora MySQL DB cluster that will use a custom parameter group. The architect creates the parameter group with the default settings and associates it with the DB cluster. After the cluster is running, the architect modifies a dynamic parameter in the parameter group and wants the change to take effect immediately without rebooting the cluster. Which action should the architect take?

Accepted Answer

Modify the parameter value and choose the immediate apply option.. For dynamic parameters in Aurora, you can modify the parameter value and choose to apply the change immediately, which takes effect without rebooting the DB cluster. This provides minimal disruption and meets the requirement. Static parameters would require a reboot, but the scenario specifies a dynamic parameter. The other options either cause unnecessary downtime or delay the change.

Answer

Modify the parameter value and wait for the next maintenance window to apply it.

Answer

Reboot the DB cluster to apply the parameter change.

Answer

Create a new parameter group with the desired value, associate it with the DB cluster, and reboot.

Question 9

A logistics company runs Amazon Aurora MySQL for a shipment-tracking service. Analysts run long-running, resource-intensive reporting queries against the same cluster that serves production traffic, causing latency spikes. The company wants to isolate reporting without changing the application's writer endpoint and wants the reporting replicas to share the same storage volume so replication lag is minimal. Which approach should a database specialist implement?

Accepted Answer

Add Aurora Replicas to the cluster and create a custom endpoint for the reporting replicas.. Aurora Replicas share the cluster's distributed storage volume, so adding replicas and grouping the reporting ones behind a custom endpoint isolates analytics with minimal replication lag while leaving the writer endpoint untouched. The reader endpoint alone cannot separate reporting from production read traffic, and non-Aurora replicas or global databases do not share storage.

Answer

Create an Amazon RDS for MySQL read replica and point reporting queries to it.

Answer

Enable Aurora Auto Scaling on the reader endpoint and rely on the reader endpoint for reporting.

Answer

Create an Aurora global database and direct reporting queries to the secondary Region's writer.

Question 10

A startup is deploying a new Amazon Aurora PostgreSQL cluster for a development environment. The team wants the cluster to be created reproducibly from a version-controlled template, including the DB subnet group, parameter group, and cluster settings, rather than through console clicks. Which approach should be used?

Accepted Answer

Write an AWS CloudFormation template that declares the DB subnet group, DB cluster parameter group, and Aurora cluster resources, and deploy it through a stack.. Declaring the Aurora cluster, DB subnet group, and cluster parameter group as resources in an AWS CloudFormation template makes the deployment declarative and reproducible. The template lives in version control, changes are reviewed before deployment, and stacks can be recreated identically across environments, which is exactly the infrastructure-as-code outcome the team needs for a development environment.

Answer

Take a manual snapshot of a configured cluster and restore it whenever a new development environment is needed.

Answer

Use AWS Trusted Advisor to check the Aurora cluster configuration and export the recommended settings as a script.

Answer

Create the cluster in the console, then use AWS Config to record the resulting resource configuration as a reusable template.

Question 11

A healthcare company stores patient records in an Amazon RDS for PostgreSQL database. The database must be encrypted at rest and in transit. The company also needs to ensure that encryption keys are rotated annually and that access to the keys is audited. Which combination of actions should a database specialist take to meet these requirements?

Accepted Answer

Enable encryption at rest using an AWS KMS customer managed key, enforce SSL connections, and enable KMS key rotation.. A customer managed KMS key enables annual rotation and provides audit trails through CloudTrail. Enforcing SSL ensures data in transit is encrypted. Together, these actions satisfy the encryption at rest, in transit, key rotation, and auditing requirements for the RDS PostgreSQL database.

Answer

Use application-level encryption for data at rest, enforce SSL connections, and manage keys in AWS Secrets Manager with rotation.

Answer

Enable encryption at rest using an AWS KMS customer managed key, but do not enforce SSL because RDS automatically encrypts data in transit.

Answer

Enable encryption at rest using the default AWS managed key for RDS, enforce SSL connections, and rely on AWS to rotate the key.

Question 12

A database specialist manages an Amazon RDS for MySQL DB instance with a read replica in the same AWS Region. The replica is used for read-heavy reporting. The specialist notices that the replica lag has been steadily increasing over the past hour and wants to identify the cause. Which action should the specialist take FIRST to diagnose the issue?

Accepted Answer

Check the ReplicaLag metric in Amazon CloudWatch for the read replica.. The ReplicaLag metric in Amazon CloudWatch is the most direct indicator of replication delay for an RDS read replica. Checking it first confirms the problem and provides data to guide further investigation, such as examining slow queries on the replica or write load on the source. Other actions are either diagnostic but less specific, or remedial and premature.

Answer

Enable enhanced monitoring on the source DB instance to capture OS-level metrics.

Answer

Create a new read replica from the source DB instance and delete the old one.

Answer

Modify the read replica to use a larger instance class to reduce lag.

Question 13

A company runs an Amazon DynamoDB table containing sensitive financial records. The security team wants to ensure that only a specific IAM role can read data from the table, and that all read requests are logged in AWS CloudTrail. The role is used by an AWS Lambda function. Which combination of actions will achieve these requirements?

Accepted Answer

Create an IAM policy that allows dynamodb:GetItem and dynamodb:Query on the table, attach it to the Lambda execution role, and enable CloudTrail data events for the table.. To restrict read access to a specific IAM role, an IAM policy granting only the necessary DynamoDB read actions (GetItem, Query) on the table resource is attached to the Lambda execution role. To log all read requests, CloudTrail data events must be enabled for the DynamoDB table, as data events capture item-level operations. This combination satisfies both the least privilege and audit logging requirements.

Answer

Create an IAM policy that denies all actions except dynamodb:GetItem and dynamodb:Query on the table, attach it to the Lambda execution role, and enable DynamoDB Accelerator (DAX) for the table.

Answer

Create an IAM policy that allows dynamodb:GetItem and dynamodb:Query on the table, attach it to the Lambda execution role, and enable DynamoDB Streams to capture read events.

Answer

Create an IAM policy that allows dynamodb:* on all tables, attach it to the Lambda execution role, and enable CloudTrail management events.

Question 14

A company is deploying a new Amazon DynamoDB table for a high-traffic application. The table must be able to handle sudden spikes in read and write traffic without manual intervention. The company wants to minimize operational overhead. Which capacity mode should be used?

Accepted Answer

On-demand capacity mode. DynamoDB on-demand capacity mode is designed for workloads with unknown or variable traffic patterns. It instantly accommodates sudden spikes in read and write activity without requiring you to specify capacity or configure auto scaling. You are charged per request, so you only pay for what you use. This mode eliminates the need for capacity planning and reduces operational overhead, making it the best choice for high-traffic applications with unpredictable spikes.

Answer

Provisioned capacity mode with global secondary indexes

Answer

Provisioned capacity mode with reserved capacity

Answer

Provisioned capacity mode with auto scaling enabled

Question 15

A database specialist is managing an Amazon DynamoDB table that uses on-demand capacity mode. The application experiences sudden bursts of read traffic, and the specialist notices that some read requests are being throttled with ProvisionedThroughputExceededException even though the table is in on-demand mode. The specialist needs to determine the cause of the throttling and mitigate it. Which factor is most likely causing the throttling?

Accepted Answer

The table has a hot partition due to an unevenly distributed partition key, causing a single partition to exceed its throughput limits.. Even in on-demand mode, DynamoDB partitions have a maximum throughput limit. A hot partition caused by an unevenly distributed partition key can lead to throttling when a single partition receives more traffic than it can handle. The solution involves designing a more uniform partition key or using techniques like write sharding to distribute the load.

Answer

The table's read capacity is set too low, and the specialist must switch to provisioned mode to set a higher capacity.

Answer

The on-demand capacity mode has a default maximum throughput of 40,000 read request units per second, and the burst exceeded that limit.

Answer

The application is using eventually consistent reads, which are throttled more aggressively than strongly consistent reads.

Question 16

A healthcare company is building a new patient records system that must store millions of documents in JSON format. The documents have varying structures, and the application requires flexible schema and the ability to query nested attributes. The database must be highly available and scale horizontally. Which AWS service is the MOST appropriate?

Accepted Answer

Amazon DocumentDB (with MongoDB compatibility). Amazon DocumentDB is designed for JSON document storage with flexible schemas and supports rich queries on nested fields. It provides the scalability and high availability required, whereas the other options are either relational, key-value, or graph databases that do not match the document-oriented requirements as closely.

Answer

Amazon DynamoDB with a single-table design

Answer

Amazon Neptune

Answer

Amazon RDS for PostgreSQL with JSONB columns

Question 17

A startup is building a mobile application that needs a fully managed, key-value database with single-digit millisecond latency and automatic scaling. The team wants to avoid managing servers and wants a simple pay-per-request pricing model. Which AWS database service should a database specialist recommend?

Accepted Answer

Amazon DynamoDB with on-demand capacity mode.. Amazon DynamoDB is a fully managed, serverless key-value and document database that provides consistent single-digit millisecond latency and scales automatically. On-demand capacity mode charges per request, eliminating capacity planning and matching the startup's pay-per-request requirement. It requires no server management, making it the correct choice for the mobile application.

Answer

Amazon Neptune with a serverless configuration.

Answer

Amazon RDS for MySQL with Provisioned IOPS storage.

Answer

Amazon ElastiCache for Redis with cluster mode enabled.

Question 18

A database administrator is responsible for an Amazon RDS for MySQL DB instance. The administrator needs to be alerted when the free storage space falls below 10% of the allocated storage. The administrator wants to receive an email notification. What is the MOST efficient way to achieve this?

Accepted Answer

Create a CloudWatch alarm on the FreeStorageSpace metric with a threshold of 10% of allocated storage, and configure an SNS topic to send email notifications.. CloudWatch alarms are the standard way to monitor RDS metrics and trigger actions. The FreeStorageSpace metric is available out-of-the-box. By setting an alarm threshold at 10% of allocated storage and linking it to an SNS topic with an email subscription, the administrator gets notified automatically. This requires minimal configuration and no custom code.

Answer

Use AWS Trusted Advisor to monitor RDS storage and configure an email notification.

Answer

Enable RDS Enhanced Monitoring and create a CloudWatch Logs subscription filter to send alerts.

Answer

Create an AWS Lambda function that queries the RDS instance for free storage space and sends an email via Amazon SES.

Question 19

A company is using Amazon RDS for Oracle and needs to implement Transparent Data Encryption (TDE) for a new DB instance. The security team wants to use AWS KMS to manage the encryption keys. Which two actions must be performed to enable TDE with KMS for the RDS for Oracle instance? (Choose two.)

Accepted Answer

Create a KMS customer managed key and grant the RDS service the necessary permissions to use it.. To enable Oracle TDE with AWS KMS on RDS, you must create a custom option group with the Oracle Transparent Data Encryption option and associate it with the DB instance. Additionally, you must create a KMS customer managed key and grant the RDS service principal permissions to use it. These two actions are required. Instance-level encryption at rest, Multi-AZ, and IAM roles for the instance are not part of this process.

Answer

Restart the DB instance in a Multi-AZ configuration to activate TDE.

Answer

Create an IAM role that allows the DB instance to access the KMS key, and attach it to the DB instance.

Answer

Modify the DB instance to enable encryption at rest using the KMS key.

Question 20

A database specialist is responsible for an Amazon DocumentDB cluster. The specialist needs to monitor the cluster's CPU utilization and set up an alarm if it exceeds 80% for 10 minutes. Which AWS service should be used to create this alarm?

Accepted Answer

Amazon CloudWatch. Amazon CloudWatch is the AWS service designed for monitoring resources and applications. It collects metrics from DocumentDB, such as CPUUtilization, and allows you to create alarms that trigger when a metric crosses a threshold for a specified duration. The other services either log API calls, route events, or provide best-practice checks, but none provide metric-based monitoring and alarms.

Answer

Amazon EventBridge

Answer

AWS Trusted Advisor

Answer

AWS CloudTrail