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

Question 1

A database administrator notices that an Amazon RDS for MySQL DB instance is experiencing high CPU utilization and increased latency during peak hours. The administrator wants to identify the queries causing the issue. Which TWO actions should be taken to diagnose the problem? (Select TWO.)

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

Accepted Answer

Enable Performance Insights on the DB instance.. Enabling Performance Insights provides database performance metrics including wait events and SQL query details, allowing identification of queries causing high CPU and latency. Option C: Enabling the slow query log captures queries that exceed a specified duration threshold, helping to pinpoint slow-running queries. Option B (Amazon DevOps Guru for RDS) is an automated service for anomaly detection and performance insights, not a direct method to identify specific queries. Option D (RDS Proxy) manages connection pooling and improves scalability, but does not identify problematic queries. Option E (RDS Enhanced Monitoring) provides OS-level metrics, not query-level details.

Answer

Enable Amazon DevOps Guru for RDS.

Answer

Use RDS Proxy to manage connections.

Answer

Enable RDS Enhanced Monitoring.

Question 2

A company is running a production Amazon Aurora MySQL-Compatible Edition database. The database has recently experienced several failovers due to replica lag. The DBA needs to implement monitoring to detect replica lag early. Which THREE metrics should be monitored to assess replication health? (Select THREE.)

Accepted Answer

DatabaseConnections. (DatabaseConnections) can indirectly indicate replication issues if application retries increase due to failovers. Option C (ReplicaLag) is the standard MySQL metric measuring replication lag. Option E (AuroraReplicaLag) is the direct Aurora-specific metric for replica lag. The other options are not directly related to replication health: ActiveTransactions (B) measures transaction volume, not replication lag, and BufferCacheHitRatio (D) is about cache efficiency.

Answer

ActiveTransactions

Answer

BufferCacheHitRatio

Question 3

A company uses Amazon DynamoDB for a highly transactional application. The application is experiencing increased latency and throttled requests. The operations team notices that the DynamoDB table's read and write capacity utilization is consistently near 100%. The table uses on-demand capacity mode. What is the MOST likely cause of the throttling?

Accepted Answer

The table has reached the per-table throughput limit for on-demand mode.. On-demand DynamoDB tables have a per-table throughput limit (e.g., 40,000 read/write units per second). When sustained traffic exceeds this limit, requests are throttled. Option B is incorrect because global table replication does not cause throttling; it replicates writes asynchronously. Option C is incorrect because DynamoDB Accelerator (DAX) is a read cache that reduces latency, but throttling still occurs if the table itself reaches its throughput limit. Option D is incorrect because adaptive capacity automatically handles hot partitions by splitting them; however, the primary cause here is hitting the on-demand throughput limit, not a partition design issue.

Answer

The table is configured as a global table and cross-region replication is causing write conflicts.

Answer

The application is not using DynamoDB Accelerator (DAX) to cache reads.

Answer

The table's partition key design is causing hot partitions, and adaptive capacity is not enabled.

Question 4

A company is running a self-managed MongoDB cluster on Amazon EC2. The cluster consists of three replica set members in different Availability Zones. The primary node recently experienced a crash, and the cluster failed over to a secondary. However, the new primary is showing significantly higher latency. The operations team wants to ensure that failover is fast and consistent. What should be done to improve the failover reliability?

Accepted Answer

Use Amazon EBS io2 Block Express volumes with provisioned IOPS.. Amazon EBS io2 Block Express volumes provide high IOPS and low latency, which can significantly reduce the time required for a secondary node to catch up and become the new primary after a failover. This improves failover reliability and reduces latency spikes. Option B is incorrect: EBS Multi-Attach is designed for shared block storage across multiple instances and is not suitable for MongoDB replica sets; using it could lead to data corruption. Option C is incorrect: while instance store volumes offer high I/O performance, they are ephemeral; if the instance fails, data is lost, making them unreliable for database workloads. Option D is incorrect: EBS snapshots are for backup and disaster recovery, not for improving failover performance.

Answer

Use Amazon EBS Multi-Attach to allow all replicas to share the same volume.

Answer

Switch to instance store volumes for better I/O performance.

Answer

Configure EBS snapshots to be taken every 5 minutes.

Question 5

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 6

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.. Increasing the allocated storage to 600 GB increases the baseline IOPS of gp2 from 900 (at 300 GB) to 1800 (at 600 GB), reducing reliance on burst credits and resolving the latency issue. This is cost-effective compared to switching to io1 (Option C), which would incur higher costs for 3000 provisioned IOPS. Option A (adding a read replica) does not help with write latency, and Option B (enabling Performance Insights) only aids diagnosis, not resolution.

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 7

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.. Enabling Performance Insights provides 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 B 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 8

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.. CloudWatch metrics such as ThrottledRequests and ConsumedWriteCapacityUnits directly indicate throttling events and capacity usage, enabling identification of throttling causes even with on-demand capacity. Option A is incorrect because AWS CloudTrail logs API calls but does not provide detailed throttling metrics at the item level. Option B is incorrect because VPC Flow Logs capture network traffic, not database-level throttling. Option D is incorrect because DynamoDB Streams capture item-level changes, not throttling events.

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 9

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. The correct metric to check for memory pressure is DatabaseMemoryUsagePercentage. This metric shows the percentage of the node's available memory that is in use, and when high it can lead to latency due to evictions or swap usage. NetworkBytesIn measures network traffic, not memory. ReplicationLag is relevant only for clusters with replicas, and CPUUtilization indicates CPU load, not memory pressure.

Answer

NetworkBytesIn

Answer

ReplicationLag

Answer

CPUUtilization

Question 10

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 DB instance has exceeded the Maximum Storage Duration setting.. Amazon RDS storage auto-scaling will not increase storage beyond the maximum storage threshold set by the user. If the instance has reached this maximum threshold, auto-scaling stops, even if free space is low. The phrase 'Maximum Storage Duration' in the option refers to this threshold. Option D is incorrect because the condition for auto-scaling is based on free space being below 10%, not on whether the maximum storage has been reached. If the maximum threshold has not been reached, auto-scaling should occur when free space is low.

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 storage usage has not reached the maximum allocated storage.

Question 11

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.. Enabling Enhanced Monitoring at the instance level provides OS-level metrics (CPU, memory, I/O) that can help identify resource bottlenecks causing high write latency on the primary instance. Option A is incorrect because switching to Amazon DynamoDB is a major architectural change, not a troubleshooting step. Option B is incorrect because adding read replicas does not reduce write latency on the primary; replicas handle read traffic, not writes. Option D is incorrect because while slow query logging can identify poorly performing queries, high write latency may also be caused by OS-level resource contention, which Enhanced Monitoring captures.

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 12

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. Performance Insights provides a dashboard to monitor active sessions and the queries they are running. Option A is incorrect because Amazon Inspector is a security assessment tool, not a monitoring tool for database sessions. Option C is incorrect because RDS Enhanced Monitoring provides OS-level metrics like CPU and memory, not database session details. Option D is incorrect because AWS CloudTrail logs API calls, not database sessions or queries.

Answer

Amazon Inspector

Answer

RDS Enhanced Monitoring

Answer

AWS CloudTrail

Question 13

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.. The correct approach is to query the STV_SLICES table. STV_SLICES provides disk usage per slice, which can identify data distribution skew. Option A is wrong because STL_QUERY stores query execution times, not distribution. Option B is wrong because STV_WLM_SERVICE_STATE shows current workload management queue state. Option D is wrong because CloudWatch CPUUtilization measures CPU load, not data distribution.

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 14

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

DatabaseConnections. The DatabaseConnections metric in Amazon CloudWatch tracks the number of active database connections. During a Multi-AZ failover, existing connections are dropped and new connections are blocked until the standby becomes the primary. By monitoring the time period when DatabaseConnections drops to zero or a low value, you can estimate the failover duration. Options A (FailoverTime) is not a valid CloudWatch metric for RDS; the actual metric is 'Failover' which is a count, not a duration. WriteLatency may increase during failover but does not directly measure downtime. ReplicaLag applies to read replicas, not Multi-AZ failover.

Answer

FailoverTime

Answer

WriteLatency

Answer

ReplicaLag

Question 15

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

Accepted Answer

ReadThrottleEvents. (ReadThrottleEvents) is the correct CloudWatch metric for monitoring throttled read requests on a DynamoDB table. Option B (ThrottledWriteEvents) tracks write throttles, not reads. Option C (SuccessfulRequestLatency) measures latency, not throttling. Option D (ConsumedReadCapacityUnits) shows read capacity consumption, not throttled requests.

Answer

ThrottledWriteEvents

Answer

SuccessfulRequestLatency

Answer

ConsumedReadCapacityUnits