DBS-C01 Monitoring and Troubleshooting Practice Test 12 — 15 Questions

Question 1

Refer to the exhibit. A DBA is troubleshooting a performance issue on an RDS for MySQL DB instance. The DBA runs the AWS CLI command shown. Based on the output, which of the following is a potential performance bottleneck?

Accepted Answer

The storage type is gp2, which may have limited IOPS performance.. The instance uses gp2 storage, which has burstable IOPS. If the burst balance is depleted, performance can degrade. The engine version is recent, Multi-AZ is not enabled, but that affects availability, not necessarily performance. DB instance status is available so no issue there.

Answer

The DB instance is not Multi-AZ, causing failover delay.

Answer

The DB instance status is 'available', meaning it is not accepting connections.

Answer

The engine version 8.0.27 has a known performance bug.

Question 2

A company runs a critical application on Amazon RDS for PostgreSQL with a Multi-AZ deployment. The application experiences intermittent connection timeouts and slow query performance. The CloudWatch metrics show that the 'ReadLatency' and 'WriteLatency' metrics are elevated during peak hours. The 'CPUUtilization' is consistently below 30%, and 'DatabaseConnections' is within limits. The 'BurstBalance' for the gp2 storage is frequently dropping to 0%. The DB instance is a db.r5.large with 300 GB of gp2 storage. The company wants to resolve the latency issues without significant cost increase. Which solution should the company implement?

Accepted Answer

Increase the allocated storage to 600 GB to increase baseline IOPS.. Option C: Increasing storage to 600 GB increases baseline IOPS from 900 to 1800, reducing reliance on burst credits. This is cost-effective compared to switching to io1. Option A: Increasing to io1 with 3000 IOPS would be more expensive. Option B: Adding a read replica does not help with write latency. Option D: Enabling Performance Insights only helps diagnose, not resolve.

Answer

Add a read replica to offload read traffic.

Answer

Enable Performance Insights to identify the root cause.

Answer

Switch the storage type to io1 with 3000 provisioned IOPS.

Question 3

A company is running Amazon RDS for MySQL and notices that the database CPU utilization is consistently above 80% during peak hours. The application performance is degrading. Which action should be taken first to troubleshoot the issue?

Accepted Answer

Enable Performance Insights to identify the queries causing high CPU usage.. Option B is correct because enabling Performance Insights provides a detailed analysis of database performance, helping to identify the root cause of high CPU utilization. Option A is wrong because increasing instance size without understanding the cause may lead to unnecessary costs. Option C is wrong because creating a read replica does not directly address CPU utilization on the primary instance. Option D is wrong because switching to a different database engine is a major change and not a troubleshooting step.

Answer

Increase the instance size of the RDS instance immediately.

Answer

Create a read replica to offload read traffic.

Answer

Switch the database engine to Amazon Aurora for better performance.

Question 4

A company has an Amazon DynamoDB table with on-demand capacity. Users report that write requests are occasionally throttled during peak hours. The application uses the AWS SDK and retries with exponential backoff. Which monitoring approach should be used to identify the cause of throttling?

Accepted Answer

Monitor CloudWatch metrics for ThrottledRequests and ConsumedWriteCapacityUnits.. Option C is correct because CloudWatch metrics such as WriteThrottleEvents, ConsumedWriteCapacityUnits, and ProvisionedWriteCapacityUnits (for on-demand, the provisioned is the maximum) help identify throttling causes. Option A is wrong because DynamoDB Streams track changes, not throttling. Option B is wrong because CloudTrail logs API calls but not throttling events at the item level. Option D is wrong because VPC Flow Logs capture network traffic, not database throttling.

Answer

Use AWS CloudTrail to monitor PutItem API calls for throttling errors.

Answer

Analyze VPC Flow Logs to check for network congestion.

Answer

Enable DynamoDB Streams and process records to monitor throttled requests.

Question 5

A developer notices that an Amazon ElastiCache for Redis cluster is experiencing high latency. The cluster uses a single node. Which CloudWatch metric should be reviewed first to determine if the issue is due to memory pressure?

Accepted Answer

DatabaseMemoryUsagePercentage. Option A is correct because the DatabaseMemoryUsagePercentage metric indicates the percentage of the node's memory used, which can cause latency if high. Option B is wrong because CPUUtilization indicates CPU load, not memory. Option C is wrong because NetworkBytesIn measures incoming network traffic. Option D is wrong because ReplicationLag only applies to clusters with replicas.

Answer

NetworkBytesIn

Answer

ReplicationLag

Answer

CPUUtilization

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 storage usage has not reached the maximum allocated storage.. Option C is correct because auto-scaling only triggers when storage usage reaches the maximum allocated storage and there is at least 10% free space remaining. Option A is wrong because Maximum Storage Duration is the maximum time the instance can run on provisioned storage before scaling. Option B is wrong because there is no minimum storage size for scaling. Option D is wrong because storage auto-scaling does not require modification to the DB instance class.

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 DB instance has exceeded the Maximum Storage Duration setting.

Question 7

A company uses Amazon DocumentDB (with MongoDB compatibility) for its application. The application is experiencing high write latency. The DB cluster has one primary instance and two replicas. Which action should be taken to identify the cause?

Accepted Answer

Enable Enhanced Monitoring and review OS-level metrics like CPU, memory, and I/O.. Option B is correct because enabling Enhanced Monitoring at the instance level provides OS-level metrics that can help identify resource bottlenecks causing high write latency. Option A is wrong because profiling queries in the slow query log may show slow queries but not necessarily latency at the OS level. Option C is wrong because creating additional replicas does not reduce write latency on the primary. Option D is wrong because switching to Amazon DynamoDB is a major architectural change, not a troubleshooting step.

Answer

Migrate the database to Amazon DynamoDB for better write performance.

Answer

Add more read replicas to distribute the load.

Answer

Enable slow query logging and analyze slow queries.

Question 8

A database administrator notices that an Amazon RDS for Oracle instance has a high number of connections, causing performance degradation. Which tool can be used to identify the active sessions and their queries?

Accepted Answer

Performance Insights. Option D is correct because Performance Insights provides a dashboard to monitor active sessions and the queries they are running. Option A is wrong because AWS CloudTrail logs API calls, not database sessions. Option B is wrong because RDS Enhanced Monitoring provides OS metrics, not database session details. Option C is wrong because Amazon Inspector is a security assessment tool.

Answer

Amazon Inspector

Answer

RDS Enhanced Monitoring

Answer

AWS CloudTrail

Question 9

A company's Amazon Redshift cluster is experiencing slow query performance. The cluster has three nodes. The administrator wants to identify if the issue is due to data distribution skew. Which approach should be used?

Accepted Answer

Query the STV_SLICES table to compare disk usage across slices.. Option A is correct because checking the STV_SLICES table shows disk usage per slice, revealing data distribution skew. Option B is wrong because the STL_QUERY table logs query text, not distribution. Option C is wrong because the STV_WLM_SERVICE_STATE table shows queue state, not distribution. Option D is wrong because CloudWatch metrics like CPUUtilization do not indicate distribution skew.

Answer

Examine the STL_QUERY table to analyze query execution times.

Answer

Check the STV_WLM_SERVICE_STATE table to see current queue state.

Answer

Review CloudWatch metrics for CPUUtilization per node.

Question 10

A company uses Amazon RDS for SQL Server with Multi-AZ deployment. During a failover test, the application experienced a longer downtime than expected. Which monitoring metric should be reviewed to understand the failover duration?

Accepted Answer

FailoverTime. Option B is correct because the FailoverTime metric in CloudWatch measures the time taken for a Multi-AZ failover. Option A is wrong because DatabaseConnections measures the number of connections, not failover time. Option C is wrong because ReplicaLag is for read replicas, not Multi-AZ. Option D is wrong because WriteLatency measures write latency, not failover duration.

Answer

WriteLatency

Answer

DatabaseConnections

Answer

ReplicaLag

Question 11

A developer needs to monitor the number of throttled read requests for a DynamoDB table. Which CloudWatch metric should be used?

Accepted Answer

ReadThrottleEvents. Option C is correct because ReadThrottleEvents counts throttled read requests. Option A is wrong because ConsumedReadCapacityUnits shows successful reads, not throttled ones. Option B is wrong because ThrottledWriteEvents counts write throttles. Option D is wrong because SuccessfulRequestLatency measures latency, not throttles.

Answer

ThrottledWriteEvents

Answer

SuccessfulRequestLatency

Answer

ConsumedReadCapacityUnits

Question 12

Which TWO CloudWatch metrics should be monitored to detect storage performance issues for an Amazon RDS for MySQL instance? (Choose two.)

Accepted Answer

WriteIOPS. Option A and Option C are correct. ReadIOPS and WriteIOPS measure the input/output operations per second, which can indicate storage performance issues. Option B (DatabaseConnections) is about connections, not storage performance. Option D (CPUUtilization) is about CPU usage. Option E (NetworkReceiveThroughput) is about network throughput.

Answer

NetworkReceiveThroughput

Answer

DatabaseConnections

Answer

CPUUtilization

Question 13

Which THREE metrics should be monitored to troubleshoot a slow Amazon Redshift query? (Choose three.)

Accepted Answer

DiskSpaceUsage. Options B, C, and D are correct. WLMQueueWaitTime measures time queries wait in queue, QueryDuration measures execution time, and DiskSpaceUsage indicates if disk spills are causing slowness. Option A (NetworkThroughput) is about network, not query performance. Option E (DatabaseConnections) is about connection count, not query speed.

Answer

DatabaseConnections

Answer

NetworkThroughput

Question 14

Which TWO actions should be taken to troubleshoot high memory usage on an Amazon ElastiCache for Redis node? (Choose two.)

Accepted Answer

Monitor the Evictions CloudWatch metric.. Options A and D are correct. Checking the evictions metric (Evictions) shows if memory is being freed due to maxmemory policy. Increasing the maxmemory parameter can alleviate memory pressure. Option B (enabling Reserved Memory) reserves memory for overhead, not a troubleshooting step. Option C (monitoring CPUUtilization) is for CPU, not memory. Option E (enabling cluster mode) is a configuration change, not a troubleshooting step.

Answer

Monitor CPUUtilization CloudWatch metric.

Answer

Enable cluster mode to distribute memory across shards.

Answer

Enable Reserved Memory parameter group setting.

Question 15

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The database experiences a sudden increase in latency and the application reports timeouts. CloudWatch shows elevated 'ReadLatency' and 'WriteLatency' metrics, while 'CPUUtilization' and 'DatabaseConnections' remain normal. Which is the MOST likely cause?

Accepted Answer

A large transaction is being processed. Option B is correct because a large transaction can cause increased latency without high CPU or connection count, as it may be waiting on disk I/O or replication. Option A is wrong because Multi-AZ failover is automatic and would show a spike then recovery. Option C is wrong because insufficient storage I/O would show in 'BurstBalance' or 'WriteIOPS' metrics, not just latency. Option D is wrong because normal CPU and connections rule out a runaway query in terms of CPU, though a query could be I/O-bound. However, a large transaction is a common cause of such symptoms.

Answer

A runaway query is consuming CPU resources

Answer

A Multi-AZ failover occurred

Answer

The database has insufficient provisioned IOPS