DBS-C01 Practice Test 32 — 15 Questions

Question 1

A company is running an Amazon Aurora MySQL-compatible edition DB cluster. The application reports that a recent schema change caused a significant increase in the number of deadlocks. Which parameter should the DBA check and possibly adjust to reduce deadlocks?

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

Accepted Answer

transaction_isolation. Deadlocks in Aurora MySQL are heavily influenced by the transaction isolation level. Lowering from REPEATABLE READ (the default) to READ COMMITTED reduces gap locking and next-key locks, which are common deadlock sources in InnoDB. The DBA should check and possibly adjust transaction_isolation.

Answer

innodb_lock_wait_timeout

Answer

autocommit

Answer

max_connections

Question 2

A database administrator is monitoring Amazon RDS for PostgreSQL using CloudWatch. The DB instance shows high CPU utilization, but the number of connections is normal. What is the most likely cause of the high CPU utilization?

Accepted Answer

There are long-running queries or missing indexes causing high CPU usage.. High CPU utilization with a normal number of connections strongly suggests the CPU is being consumed by query execution rather than connection overhead. Long-running queries, missing indexes causing full table scans, or inefficient query plans are the most common causes of sustained high CPU on RDS PostgreSQL.

Answer

The DB instance has a low burst balance for gp2 storage.

Answer

The instance is low on memory and is swapping.

Answer

The DB instance has a large number of Read Replicas.

Question 3

A company needs to migrate an on-premises Oracle database to AWS with minimal changes to the application code. The application uses complex stored procedures and has high availability requirements. Which database service should be used?

Accepted Answer

Amazon RDS for Oracle. Amazon RDS for Oracle is the correct choice because it provides native Oracle compatibility, supporting complex stored procedures, PL/SQL, and existing application code with minimal changes. It also offers Multi-AZ deployments for high availability, meeting the requirement without requiring a complete rewrite.

Answer

Amazon DynamoDB

Answer

Amazon Redshift

Answer

Amazon Aurora PostgreSQL

Question 4

A company notices that its Aurora MySQL cluster has a high number of locks and deadlocks. The application uses read replicas for read scaling. What is the MOST likely cause?

Accepted Answer

Long-running transactions on the writer instance. Long-running transactions on the writer instance hold locks for extended periods, increasing the probability of lock contention and deadlocks. Option A is incorrect because Performance Insights is a monitoring tool and does not cause locks or deadlocks. Option B is incorrect because mismatched instance sizes may affect performance but do not directly cause locks or deadlocks. Option D is incorrect because Aurora read replicas are read-only and cannot perform write operations.

Answer

Performance Insights is enabled

Answer

The writer and reader instances are of different sizes

Answer

Read replicas are performing write operations

Question 5

Refer to the exhibit. An engineer runs the CLI command to check security groups attached to the RDS instance 'mydb'. The output shows only one security group. The engineer wants to ensure that only traffic from an application server with IP 10.0.1.5 is allowed to the database port 3306. Which security group rule should be added?

Accepted Answer

Add an inbound rule to allow traffic from 10.0.1.5/32 on port 3306.. To allow only the application server at 10.0.1.5 to reach the RDS instance on MySQL port 3306, an inbound rule must be added to the RDS security group permitting traffic from 10.0.1.5/32 on port 3306. Security groups are stateful, so return traffic is automatically allowed without an outbound rule. This precisely scopes access to the single application server.

Answer

Add an inbound rule to allow traffic from 10.0.1.5/32 on port 80.

Answer

Add an outbound rule to allow traffic to 10.0.1.5 on port 3306.

Answer

Add an inbound rule to allow traffic from 0.0.0.0/0 on port 3306.

Question 6

An Amazon DynamoDB table is experiencing throttled write requests. The table uses provisioned capacity with auto-scaling enabled. Which THREE factors could contribute to throttling despite auto-scaling?

Accepted Answer

Auto-scaling maximum capacity is set too low. Auto-scaling can prevent throttling only if the maximum capacity is set appropriately and traffic patterns are predictable. Option B is correct because if the auto-scaling maximum capacity is set too low, the table cannot scale enough to handle the write demand. Option C is correct because auto-scaling reacts to sustained traffic but cannot instantly accommodate a sudden traffic spike that exceeds the maximum capacity. Option E is correct because even with auto-scaling, an uneven partition key distribution can cause a single partition to exceed its throughput capacity, leading to throttling. Option A is incorrect; a global secondary index with the same partition key does not inherently cause throttling on the base table. Option D is incorrect because eventually consistent reads affect read capacity, not write capacity, and do not cause write throttling.

Answer

Global secondary index is defined with same partition key

Answer

Use of eventually consistent reads

Question 7

A financial services company stores sensitive data in an Amazon DynamoDB table. The security team requires that all data at rest be encrypted with a customer-managed key that is rotated automatically every 12 months. The company also needs to audit key usage. Which solution meets these requirements?

Accepted Answer

Enable encryption at rest using an AWS KMS customer-managed CMK. Configure automatic key rotation with a 12-month period. Use AWS CloudTrail to audit key usage.. DynamoDB supports encryption at rest with AWS KMS customer-managed CMKs. Automatic key rotation every 12 months is a feature of KMS for CMKs. CloudTrail logs KMS API calls for auditing. Option A is incorrect because SSE-S3 is for S3, not DynamoDB. Option B is incorrect because CloudHSM does not provide automatic key rotation every 12 months and requires application-side encryption. Option C is incorrect because the default DynamoDB encryption uses an AWS owned key, which is not customer-managed and rotates automatically every 3 years, not 12 months. Option D is correct: it uses a customer-managed CMK with yearly rotation and CloudTrail for auditing.

Answer

Use server-side encryption with S3-managed keys (SSE-S3) for the DynamoDB table.

Answer

Use AWS CloudHSM to generate and store the encryption key. Configure the application to encrypt data before writing to DynamoDB.

Answer

Enable encryption at rest using the default DynamoDB encryption option (AWS owned key). Use AWS CloudTrail to audit key usage.

Question 8

A company uses Amazon DynamoDB for its critical application. The security team requires that all access to DynamoDB tables be logged and monitored for suspicious activity. The company also needs to be alerted when a user deletes a table. Which combination of AWS services should be used?

Accepted Answer

AWS CloudTrail and Amazon CloudWatch Events.. AWS CloudTrail logs all API activity on DynamoDB tables, including DeleteTable calls, providing the audit trail. Amazon CloudWatch Events (now Amazon EventBridge) can match the DeleteTable API call and trigger an alert via SNS or Lambda. Together they satisfy logging, monitoring, and alerting on table deletion.

Answer

AWS CloudTrail and Amazon DynamoDB Streams.

Answer

AWS Config and Amazon Simple Notification Service (SNS).

Answer

Amazon VPC Flow Logs and Amazon CloudWatch Logs.

Question 9

A startup is building a mobile app backend using Amazon DynamoDB. They anticipate unpredictable traffic spikes. Which DynamoDB feature should they use to handle the spikes without manual intervention?

Accepted Answer

Enable DynamoDB Auto Scaling for read and write capacity.. DynamoDB Auto Scaling (option B) automatically adjusts the provisioned read and write capacity based on actual traffic patterns, using CloudWatch alarms and the Application Auto Scaling service. This allows the startup to handle unpredictable spikes without manual intervention, as the service will increase capacity during high demand and decrease it during low demand, ensuring consistent performance and cost efficiency.

Answer

Use DynamoDB Accelerator (DAX) as a cache layer.

Answer

Set up a TTL (Time to Live) to automatically expire old items.

Answer

Implement DynamoDB Global Tables for multi-region replication.

Question 10

Which THREE components are required to set up IAM database authentication for an Amazon RDS for MySQL DB instance? (Choose three.)

Accepted Answer

An IAM role that the application can assume.. The three required components for setting up IAM database authentication for an Amazon RDS for MySQL DB instance are: (A) an IAM role that the application can assume to retrieve an authentication token from IAM; (C) a database user that is mapped to the IAM role in the RDS MySQL database; and (D) a DB parameter group with `require_secure_transport` set to ON to enforce SSL/TLS connections, which are mandatory for IAM authentication. Option B (AWS KMS key) is not required because the authentication token is signed by IAM, not encrypted with KMS. Option E (RDS Proxy) is optional and not a requirement; while it can provide connection pooling, it is not needed to set up IAM authentication itself.

Answer

An AWS KMS key to encrypt the authentication token.

Answer

An RDS Proxy to manage connections.

Question 11

Which TWO actions can be used to encrypt an existing unencrypted Amazon RDS for MySQL DB instance? (Choose 2.)

Accepted Answer

Create a new encrypted DB instance and migrate data using database dump and restore.. To encrypt an existing unencrypted RDS for MySQL DB instance, you cannot modify the instance directly (option E is incorrect). You can either take a snapshot, copy it with encryption enabled, and restore from the encrypted snapshot (option D), or create a new encrypted DB instance and migrate data using database dump and restore (option C). Option A is incorrect because creating a read replica with encryption enabled does not encrypt the source instance. Option B is incorrect because enabling SSL encrypts data in transit, not at rest.

Answer

Create a read replica with encryption enabled.

Answer

Enable SSL on the DB instance.

Answer

Modify the DB instance and enable encryption.

Question 12

A database administrator needs to audit all SQL statements executed on an Amazon Aurora MySQL DB cluster, including SELECT queries. Which AWS service should be used to capture and store these logs?

Accepted Answer

Amazon RDS Database Activity Streams. Amazon RDS Database Activity Streams (Option A) is the correct service to capture and store audit logs of SQL statements, including SELECT queries, on an Aurora MySQL DB cluster. It streams database activity to Amazon CloudWatch Logs and Amazon Kinesis Data Streams for further analysis and storage. Option B (Amazon RDS Enhanced Monitoring) provides OS-level metrics, not SQL statements. Option C (Amazon CloudWatch Logs) can store logs but does not capture SQL statements directly; it requires a source like Database Activity Streams. Option D (Amazon RDS Performance Insights) monitors database performance, not SQL audit logs.

Answer

Amazon RDS Enhanced Monitoring

Answer

Amazon CloudWatch Logs

Answer

Amazon RDS Performance Insights

Question 13

A company needs to store session state for a web application that runs on Amazon EC2 instances behind an Application Load Balancer. The session data is small (less than 1 KB per user) and must be highly available with low latency. Which AWS database service is best for this use case?

Accepted Answer

Amazon ElastiCache for Redis. Amazon ElastiCache for Redis is the best choice because it provides an in-memory data store with sub-millisecond latency, ideal for storing small session state data (less than 1 KB per user). Redis supports key-value operations with built-in data expiration (TTL), making it perfect for session management. Its replication and automatic failover capabilities ensure high availability, meeting the application's requirements.

Answer

Amazon S3

Answer

Amazon DynamoDB

Answer

Amazon RDS for MySQL

Question 14

A company is using Amazon RDS for MySQL and needs to monitor for slow queries. Which TWO AWS services can be used to capture and analyze slow query logs? (Choose TWO.)

Accepted Answer

Amazon RDS Performance Insights. Amazon RDS Performance Insights (B) is correct because it provides a visual, query-level view of database load and can identify the top SQL statements contributing to load, including slow-running queries on RDS for MySQL, without requiring manual log parsing. Amazon CloudWatch Logs (E) is correct because RDS for MySQL can publish the slow query log to CloudWatch Logs, where you can search, filter, and analyze entries using metric filters and Logs Insights queries. Amazon S3 (A) is not a monitoring or log-analysis service; it is object storage and would only hold exported logs, not capture or analyze slow queries directly. AWS Config (C) tracks resource configuration changes and compliance, not database query performance. AWS CloudTrail (D) records AWS API activity and management events, not the SQL statements executed against a MySQL database.

Answer

Amazon S3

Answer

AWS Config

Answer

AWS CloudTrail

Question 15

A company is running an Amazon RDS for SQL Server instance and wants to automate the patching of the database engine. Which AWS service should be used?

Accepted Answer

Amazon RDS Maintenance Window. Amazon RDS Maintenance Windows are the built-in mechanism for applying engine patches, minor version upgrades, and OS updates to RDS instances. You define a weekly window, and RDS automatically applies mandatory patches during that window (or you can apply them manually). This is the AWS-native way to automate RDS for SQL Server engine patching.

Answer

AWS Config

Answer

Amazon RDS Automated Backups

Answer

AWS Systems Manager Patch Manager