DBS-C01 Practice Exam 60 — 20 Questions

Question 1

A company uses Amazon ElastiCache for Redis as a caching layer for a web application. They observe a sudden increase in CPU utilization on the cache cluster, and the application experiences higher latency. Which action should be taken to diagnose the issue?

Accepted Answer

Monitor Amazon CloudWatch metrics for the ElastiCache cluster to identify the cause.. Option A is correct because CloudWatch metrics like CPUUtilization and CacheHits are the first step to diagnose. Option B is wrong because increasing node size is a solution, not a diagnostic step. Option C is wrong because ElastiCache does not have a built-in query profiler. Option D is wrong because disabling persistence is unrelated.

Answer

Enable query profiling on the ElastiCache cluster.

Answer

Disable persistence to reduce CPU overhead.

Answer

Immediately scale up to a larger node type.

Question 2

A team is troubleshooting an Amazon RDS for SQL Server instance that is running out of storage. The instance uses General Purpose SSD (gp2) storage. The team wants to increase storage without downtime. Which action should they take?

Accepted Answer

Modify the DB instance to increase allocated storage.. Option D is correct because RDS supports modifying storage settings without downtime, and the change occurs during the next maintenance window. Option A is wrong because creating a snapshot does not increase storage. Option B is wrong because gp3 is not supported for SQL Server. Option C is wrong because read replicas do not increase storage on the primary.

Answer

Migrate to gp3 storage.

Answer

Add a read replica to offload queries.

Answer

Take a snapshot and restore to a larger instance.

Question 3

A company uses Amazon CloudWatch to monitor an RDS for Oracle instance. They want to receive an alert when the database connection count exceeds 90% of the maximum connections. Which CloudWatch metric should be used to create the alarm?

Accepted Answer

DatabaseConnections. Option A is correct because DatabaseConnections tracks the number of client connections. Option B is wrong because ActiveTransactions measures transactions. Option C is wrong because NetworkThroughput measures network traffic. Option D is wrong because ReadIOPS measures disk I/O.

Answer

ActiveTransactions

Answer

ReadIOPS

Answer

NetworkThroughput

Question 4

A database administrator notices that an Amazon RDS for SQL Server DB instance has been in the 'storage-optimization' state for several hours after modifying the storage type from gp2 to io1. What should the administrator do to resolve this?

Accepted Answer

Wait for the storage optimization to complete.. Option B is correct because 'storage-optimization' is a normal state that occurs when modifying the storage configuration, and no action is required. Option A is incorrect because rebooting does not speed up the optimization. Option C is incorrect because there is no need to restore from snapshot. Option D is incorrect because the modification is in progress, and there is no need to cancel it.

Answer

Restore from the latest snapshot and reapply the modification.

Answer

Cancel the modification by modifying the DB instance back to gp2.

Answer

Reboot the DB instance.

Question 5

Which THREE metrics should be monitored in Amazon CloudWatch to detect a potential memory leak in an Amazon RDS for SQL Server instance? (Choose three.)

Accepted Answer

DatabaseConnections. Options B, C, and E are correct. FreeableMemory shows available memory. SwapUsage indicates memory pressure. DatabaseConnections can increase if connections are not closed properly. Option A is incorrect because CPUUtilization is not a memory metric. Option D is incorrect because ReadIOPS relates to I/O.

Answer

CPUUtilization

Answer

ReadIOPS

Question 6

A company is running a production Amazon RDS for MySQL DB instance. The application team reports intermittent high latency and connection timeouts. A quick check shows that the DB instance's CPU utilization is consistently above 90% during peak hours. The database size is 500 GB and the instance class is db.r5.large. Which combination of actions should a database specialist take to resolve the performance issue?

Accepted Answer

Scale up the DB instance to db.r5.xlarge and review slow query logs to optimize poorly performing queries.. Option B is correct because scaling up the DB instance to db.r5.xlarge increases compute capacity, which directly addresses high CPU utilization. Additionally, reviewing slow query logs can identify inefficient queries causing CPU spikes. Option A is wrong because enabling Multi-AZ does not increase compute capacity; it only provides high availability. Option C is wrong because enabling Performance Insights helps diagnose but does not resolve the issue. Option D is wrong because increasing the allocated storage does not affect CPU performance.

Answer

Increase the allocated storage to 1 TB and enable auto-scaling for storage.

Answer

Enable Multi-AZ and increase the allocated storage to 1 TB to improve I/O performance.

Answer

Enable Performance Insights and create a CloudWatch alarm to notify when CPU exceeds 80%.

Question 7

A DBA is investigating a sudden increase in database connections to an Amazon RDS for SQL Server instance. The application is running on Amazon EC2 instances behind an Application Load Balancer. Which tool can provide real-time information about active connections?

Accepted Answer

Amazon RDS Performance Insights. Option C is correct because RDS Performance Insights shows active session information including connections. Option A is wrong because CloudTrail tracks API calls, not connections. Option B is wrong because VPC Flow Logs track network traffic, not database connections. Option D is wrong because Trusted Advisor gives best practice checks, not real-time connections.

Answer

AWS Trusted Advisor

Answer

VPC Flow Logs

Answer

AWS CloudTrail

Question 8

A database administrator notices that an Amazon RDS for MySQL instance's CPU utilization is consistently above 80% during peak hours. The DB instance is a db.r5.large with 16 GB memory and 500 GB gp2 storage. The application is a read-intensive web application. Which action is MOST effective to reduce CPU load without significant cost increase?

Accepted Answer

Create a read replica and redirect read traffic to it. Option B is correct because creating a read replica offloads read traffic from the primary instance, reducing CPU utilization without requiring a larger instance or more storage. Option A increases cost significantly. Option C may not help if the issue is CPU, not I/O. Option D increases storage but does not directly reduce CPU.

Answer

Increase the instance size to db.r5.xlarge

Answer

Enable Performance Insights to identify slow queries and optimize them

Answer

Increase the allocated storage to 1000 GB to improve I/O performance

Question 9

A database administrator is troubleshooting a performance issue on an Amazon Aurora MySQL cluster. The application is experiencing high latency on write operations. Which TWO CloudWatch metrics should the administrator analyze to identify the root cause?

Accepted Answer

DMLThroughput. Option A (DMLThroughput) measures the rate of write operations. Option D (CommitLatency) measures the time to commit transactions, which directly affects write latency. Option B is incorrect because it is a read metric. Option C is incorrect because it measures storage. Option E is incorrect because it is a read latency metric.

Answer

ReadLatency

Answer

SelectLatency

Answer

FreeableMemory

Question 10

A company uses Amazon DynamoDB with auto scaling enabled. They notice that a table's write capacity is frequently throttled during a specific hour each day. The access pattern is uniform across partitions. Which action would resolve the throttling without manual intervention?

Accepted Answer

Increase the minimum provisioned capacity in auto scaling.. Option C is correct because auto scaling should increase capacity to meet demand, but if it is not scaling fast enough, adjusting the scaling policy can help. Option A is wrong because disabling auto scaling is not a solution. Option B is wrong because the pattern is uniform, so partitioning is not the issue. Option D is wrong because DAX is for reads, not writes.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes.

Answer

Disable auto scaling and set a fixed higher capacity.

Answer

Create a larger number of partitions by splitting the table.

Question 11

A company is experiencing high read latency on their Amazon RDS for MySQL Multi-AZ DB instance. The application performs many small, random reads. Which configuration change would most likely reduce the read latency without incurring additional compute costs?

Accepted Answer

Enable Multi-AZ DB cluster deployment with two readable standby instances and route read traffic to the standby.. Option B is correct because Amazon RDS provides the Multi-AZ DB cluster deployment option which includes two readable standby instances, allowing read traffic to be offloaded to the standby to reduce load on the primary. Option A is incorrect because increasing the instance size would increase compute costs. Option C is incorrect because enabling Performance Insights does not reduce read latency. Option D is incorrect because increasing the allocated storage does not directly improve read latency for random reads.

Answer

Increase the allocated storage size to improve I/O throughput.

Answer

Enable Performance Insights to monitor and optimize queries.

Answer

Increase the instance size from db.r5.large to db.r5.xlarge.

Question 12

A company is using Amazon DynamoDB with global tables to support a multi-region application. They notice that writes to the table in us-east-1 are not replicating to the table in eu-west-1. The replication lag metric shows increasing values. What is the most likely cause?

Accepted Answer

The table in eu-west-1 has been removed as a replica region from the global table configuration.. Option C is correct because DynamoDB global tables replicate writes asynchronously; if the replica table in eu-west-1 is not properly configured as a global table replica, replication will fail. Option A is incorrect because global tables do not require VPC endpoints. Option B is incorrect because auto scaling does not affect replication. Option D is incorrect because DynamoDB Streams are used for global tables replication, but disabling them would stop replication, not cause lag.

Answer

The table in eu-west-1 has a lower write capacity and is throttling incoming writes.

Answer

DynamoDB Streams is disabled on the table in us-east-1.

Answer

The DynamoDB table in us-east-1 is not accessible from eu-west-1 due to VPC restrictions.

Question 13

Which TWO AWS services can be used to monitor the performance of an Amazon DynamoDB table and send alerts when throttling occurs? (Choose two.)

Accepted Answer

Amazon CloudWatch Alarms. Options A and D are correct. Amazon CloudWatch provides metrics and alarms for DynamoDB. AWS CloudTrail logs API calls but does not monitor performance metrics. Option B is incorrect because AWS Config tracks resource changes, not performance. Option C is incorrect because VPC Flow Logs capture network traffic. Option E is incorrect because Amazon Inspector is a security assessment service.

Answer

Amazon Inspector

Answer

VPC Flow Logs

Answer

AWS Config

Question 14

A database specialist is troubleshooting a degraded Amazon Aurora MySQL database cluster. The primary instance is showing elevated read latency and the replica lag is increasing. The DB cluster has one writer and one reader instance. The writer instance is using 90% of its allocated memory, and the reader instance is using 70%. Which action is most likely to reduce read latency and replica lag?

Accepted Answer

Increase the reader instance size to provide more buffer pool memory.. Option D is correct because increasing the instance size of the reader provides more memory for the buffer pool, improving read performance and reducing replica lag. Option A is wrong because increasing the writer instance size does not directly help read latency on the reader. Option B is wrong because adding another reader does not help if the existing reader is under-resourced. Option C is wrong because increasing storage does not directly improve memory or query performance.

Answer

Increase the allocated storage for the cluster to improve I/O throughput.

Answer

Increase the writer instance size to provide more memory for write operations.

Answer

Add a second reader instance to distribute the read load.

Question 15

An e-commerce application uses Amazon Aurora MySQL. During a flash sale, the database experiences a surge in write operations, and the application reports 'Lock wait timeout exceeded' errors. The DBA suspects a long-running transaction is blocking others. Which AWS tool or feature should the DBA use to identify the blocking transaction?

Accepted Answer

Amazon Aurora Performance Insights with the 'Wait for lock' dimension. Option D is correct because Aurora's Performance Insights with the 'Wait for lock' dimension can identify blocking sessions. Option A is wrong because Amazon Inspector is a security assessment tool. Option B is wrong because CloudWatch Logs Insights can analyze logs but does not directly identify blocking transactions. Option C is wrong because Enhanced Monitoring provides OS-level metrics, not database lock information.

Answer

Amazon Inspector

Answer

CloudWatch Logs Insights

Answer

Amazon RDS Enhanced Monitoring

Question 16

A company is using Amazon RDS for SQL Server with Multi-AZ. The application experiences a brief interruption during a planned maintenance window. The DBA wants to verify that the failover occurred correctly. Which set of metrics should the DBA examine?

Accepted Answer

DatabaseConnections and ReplicaLag. Option D is correct because a failover results in a brief downtime (DatabaseConnections drop to zero) followed by a switch from master to standby (ReplicaLag disappears). Option A is wrong because WriteIOPS and ReadIOPS may change but not specifically indicate failover. Option B is wrong because FreeStorageSpace does not change during failover. Option C is wrong because NetworkThroughput may fluctuate but is not a direct indicator of failover.

Answer

FreeStorageSpace on the primary instance

Answer

WriteIOPS and ReadIOPS for both instances

Answer

NetworkThroughput on the replica instance

Question 17

A developer is using AWS Database Migration Service (DMS) to migrate a database from on-premises to Amazon RDS. The migration task is failing with 'Insufficient memory' error. Which resource should be increased to resolve this?

Accepted Answer

Increase the size of the DMS replication instance.. Option A is correct because the DMS replication instance may have insufficient memory. Increasing its size provides more memory. Option B is wrong because source database memory is not controlled by DMS. Option C is wrong because target RDS instance memory may not be the bottleneck. Option D is wrong because S3 is not involved in the DMS process by default.

Answer

Increase the memory on the source database.

Answer

Increase the Amazon S3 bucket size for staging.

Answer

Increase the memory on the target RDS instance.

Question 18

A database administrator notices that an Amazon RDS for MySQL instance is using 100% of its allocated storage. Which action should be taken first to prevent the instance from becoming inaccessible?

Accepted Answer

Modify the DB instance to increase allocated storage.. Option B is correct because increasing storage is immediate and prevents the instance from going into storage-full state. Option A is wrong because deleting logs may free space temporarily but is not a scalable solution. Option C is wrong because archiving to S3 does not free space. Option D is wrong because it does not solve the immediate issue.

Answer

Create a snapshot and archive it to Amazon S3.

Answer

Delete old binary logs to free up space.

Answer

Reboot the DB instance.

Question 19

An administrator is troubleshooting an Amazon RDS for PostgreSQL instance that is experiencing high CPU utilization. The administrator has enabled Performance Insights. Which metric should be examined first to identify the queries consuming the most CPU?

Accepted Answer

db.load.avg. Option B is correct because the 'db.load.avg' metric in Performance Insights shows the average number of active sessions, which helps identify queries causing high load. Option A is incorrect because 'db.cpu.avg' is not a standard Performance Insights metric. Option C is incorrect because 'db.sessions' is not a standard metric. Option D is incorrect because 'db.bytes_sent' relates to network throughput, not CPU.

Answer

db.sessions

Answer

db.cpu.avg

Answer

db.bytes_sent

Question 20

Refer to the exhibit. An IAM policy is attached to a user who is attempting to run a Scan operation on the Orders table using the AWS CLI. The Scan operation fails with an AccessDeniedException. What is the most likely reason?

Accepted Answer

The 'ForAllValues:StringEquals' condition set operator prevents the Scan operation because it requires all leading keys to match a single value, which is impossible for a Scan.. Option D is correct. The condition 'dynamodb:LeadingKeys' applies only to Query and Scan operations when the condition key is used to restrict partition key values. However, the condition 'ForAllValues:StringEquals' requires that all leading keys in the request match the specified value. For a Scan operation without a specific partition key, the condition cannot be satisfied, leading to denial. Option A is incorrect because the resource ARN includes the table name, so it is valid. Option B is incorrect because the policy allows Scan action. Option C is incorrect because the condition is on LeadingKeys, not on the table.

Answer

The resource ARN does not include the table name.

Answer

The Scan action is not allowed in the policy.

Answer

The condition requires the partition key to be 'CustomerID', but the Scan operation does not specify a partition key.