DBS-C01 Monitoring and Troubleshooting Practice Test 4 — 15 Questions

Question 1

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 2

Which TWO actions can help reduce Amazon RDS for MySQL replication lag between a primary instance and a read replica? (Choose two.)

Accepted Answer

Reduce the number of write-heavy DML statements on the primary.. Options A and D are correct. Increasing the replica instance size gives it more resources to apply changes. Reducing write-heavy DML on the primary reduces the volume of changes to replicate. Option B is incorrect because enabling Multi-AZ on the primary does not reduce lag. Option C is incorrect because binary logging is required for replication. Option E is incorrect because increasing the replica's allocated storage does not directly reduce lag.

Answer

Increase the allocated storage for the read replica.

Answer

Enable Multi-AZ on the primary instance.

Answer

Disable binary logging on the primary instance.

Question 3

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 4

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 5

Refer to the exhibit. A database administrator runs the AWS CLI command to describe events for an RDS instance. Which conclusion is most likely correct based on the output?

Accepted Answer

The DB instance experienced a Multi-AZ failover and subsequently restarted.. Option C is correct. The output shows a failover event followed by a restart, which is typical after a failover. Option A is incorrect because the events show a failover, not a manual restart. Option B is incorrect because the failover was completed, not failed. Option D is incorrect because there is no indication of a snapshot restore.

Answer

The Multi-AZ failover failed and the instance restarted.

Answer

The DB instance was manually restarted by an administrator.

Answer

The DB instance was restored from a snapshot and then restarted.

Question 6

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.

Question 7

Refer to the exhibit. A database administrator retrieves CloudWatch metrics for an RDS instance. What is the trend of CPU utilization during the monitored period?

Accepted Answer

CPU utilization is increasing over time.. Option B is correct. The average CPU utilization increases from 75.5% to 98.2% over the hour, indicating a steady increase. Option A is incorrect because it is not decreasing. Option C is incorrect because it is not constant. Option D is incorrect because it does not fluctuate; it increases monotonically.

Answer

CPU utilization is decreasing over time.

Answer

CPU utilization is constant around 90%.

Answer

CPU utilization fluctuates randomly.

Question 8

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 9

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 10

A company is using Amazon DynamoDB for a gaming leaderboard application. Recently, users have experienced increased latency when updating scores. The DynamoDB table has on-demand capacity mode. The application performs UpdateItem calls with a condition expression. Which action is most likely to reduce the latency?

Accepted Answer

Ensure that there are no throttled requests in the CloudWatch metrics and verify that the table is not experiencing hot partitions.. Option A is correct because with on-demand capacity, DynamoDB can handle sudden traffic spikes without throttling. Increasing read capacity is not applicable because on-demand mode automatically adjusts. Optimistic locking is already used implicitly with condition expressions. Adding a global secondary index does not directly reduce UpdateItem latency.

Answer

Add a global secondary index (GSI) with the score as the sort key to improve update performance.

Answer

Switch the table to provisioned capacity and increase the read capacity units to handle peak load.

Answer

Disable conditional writes to reduce the overhead of condition expression evaluation.

Question 11

A database specialist is investigating a sudden increase in Amazon RDS for PostgreSQL connections. The DB instance's CloudWatch metric DatabaseConnections shows a spike from 100 to 500 within minutes. The application connects using a connection pool. Which step should the specialist take first to mitigate the issue while preserving application availability?

Accepted Answer

Modify the DB parameter group to reduce the max_connections value and reboot the instance to apply changes.. Option C is correct because reducing the maximum connections in the parameter group and rebooting immediately limits the active connections, preventing the database from being overwhelmed. Option A is wrong because modifying the security group does not affect the number of connections. Option B is wrong because increasing the instance size may help but takes time to provision. Option D is wrong because terminating all connections will disrupt the application.

Answer

Use the RDS console to terminate all active connections and then restart the database.

Answer

Modify the security group to restrict inbound traffic to the database.

Answer

Increase the DB instance size to handle more connections.

Question 12

A company is using Amazon ElastiCache for Redis as a caching layer for a web application. The application team reports that cache miss rates have increased significantly, causing higher database load. The Redis cluster has two nodes (one primary, one replica) with the default eviction policy of noeviction. Which action should the database specialist recommend to reduce cache misses?

Accepted Answer

Change the eviction policy to allkeys-lru to allow Redis to evict less recently used keys.. Option B is correct because changing the eviction policy to allkeys-lru allows Redis to evict less frequently used keys when memory is full, reducing cache misses. Option A is wrong because adding more nodes does not solve the eviction issue if the policy prevents eviction. Option C is wrong because increasing the memory of existing nodes only delays the problem. Option D is wrong because enabling persistence does not help with memory management.

Answer

Increase the memory of existing nodes to accommodate more keys.

Answer

Enable AOF persistence to improve cache durability.

Answer

Add more read replicas to distribute the cache load.

Question 13

A database specialist needs to monitor the number of deadlocks occurring in an Amazon RDS for SQL Server DB instance. Which CloudWatch metric should be used?

Accepted Answer

Deadlocks. Option A is correct because Deadlocks is a specific metric in Amazon RDS for SQL Server that tracks deadlock occurrences. Option B is wrong because it is a generic metric. Option C is wrong because it is for blocking, not deadlocks. Option D is wrong because it is for lock waits.

Answer

BlockedTransactions

Answer

DatabaseConnections

Answer

LockWaits

Question 14

A company is using Amazon DocumentDB (with MongoDB compatibility) for a content management system. The application team notices that write operations are taking longer than usual. CloudWatch metrics show high WriteLatency and a growing number of documents in the oplog. Which step should the database specialist take to troubleshoot the issue?

Accepted Answer

Check the CPU and memory utilization of the secondary instance and consider scaling it up.. Option D is correct because high WriteLatency and growing oplog suggest that the secondary instance is too slow to apply operations, causing replication lag. Checking the secondary's metrics helps diagnose. Option A is wrong because enabling Multi-AZ does not directly address write latency. Option B is wrong because increasing the instance class may help but should be done after diagnosis. Option C is wrong because increasing storage does not improve write performance.

Answer

Enable Multi-AZ on the cluster to offload reads to the standby.

Answer

Increase the instance size of the primary instance to handle more writes.

Answer

Increase the allocated storage to improve I/O throughput.

Question 15

A company is using Amazon Redshift for data warehousing. The data engineering team notices that queries are taking longer than expected. The cluster has two nodes of type dc2.large. The database specialist checks the system tables and finds that many queries are using the disk for temporary storage. Which action should the specialist take to improve query performance?

Accepted Answer

Upgrade the cluster to a node type with more memory, such as ra3.xlplus.. Option B is correct because the need for temporary storage on disk indicates insufficient memory. Upgrading to a node type with more memory (such as ra3 nodes) reduces disk spills. Option A is wrong because increasing the number of nodes does not increase per-node memory. Option C is wrong because adding distribution keys may not reduce memory usage. Option D is wrong because enabling concurrency scaling does not address memory issues.

Answer

Add distribution keys to the tables to improve data distribution.

Answer

Enable concurrency scaling to offload queries to additional clusters.

Answer

Increase the number of nodes to three to distribute the workload.