DBS-C01 Practice Exam 62 — 20 Questions

Question 1

A database team notices that the Amazon Aurora MySQL-Compatible DB cluster is experiencing frequent failovers during peak hours. The failover events are not correlated with any maintenance windows or manual interventions. Which metric in Amazon CloudWatch should be investigated first to identify the root cause?

Accepted Answer

WriteIOPS.. Option C is correct because a high volume of write operations can cause the primary instance to become overloaded, leading to failover. Option A is incorrect because DatabaseConnections alone does not directly cause failover. Option B is incorrect because ReadLatency is a symptom, not a direct cause of failover. Option D is incorrect because FreeableMemory is not a typical cause of failover.

Answer

FreeableMemory.

Answer

DatabaseConnections.

Answer

ReadLatency.

Question 2

A company is running a production Amazon RDS for Oracle DB instance. The database specialist is setting up monitoring to detect and troubleshoot performance issues. Which TWO metrics should be used to identify whether the database is experiencing I/O bottlenecks?

Accepted Answer

ReadLatency. ReadLatency and WriteLatency directly measure the time taken for I/O operations. High values indicate I/O bottlenecks. DatabaseConnections and CPUUtilization measure other resources. FreeStorageSpace indicates storage capacity, not performance.

Answer

DatabaseConnections

Answer

CPUUtilization

Answer

FreeStorageSpace

Question 3

A database specialist is troubleshooting a performance issue on a self-managed PostgreSQL database that they plan to migrate to Amazon RDS. The database has a high number of 'idle in transaction' connections. What is the impact of these connections on the database?

Accepted Answer

They hold locks and prevent cleanup of dead tuples, leading to bloat.. Option D is correct because idle-in-transaction connections hold locks and can cause bloat, reducing performance. Option A is wrong because they do not prevent new connections from being established. Option B is wrong because CPU usage is low for idle connections. Option C is wrong because they do not affect disk I/O directly.

Answer

They increase CPU usage due to constant polling.

Answer

They prevent new connections from being established.

Answer

They cause increased disk I/O from write-ahead logging.

Question 4

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.)

Accepted Answer

Enable Performance Insights on the DB instance.. Option A: Enabling Performance Insights provides a performance schema and wait events to identify problematic queries. Option C: Enabling the slow query log captures queries that take longer than a specified time, helping to pinpoint slow queries. Option B: RDS Enhanced Monitoring is for OS-level metrics, not query-level. Option D: Amazon DevOps Guru is for broader anomaly detection, not specific query identification. Option E: RDS Proxy is for connection pooling, not query analysis.

Answer

Enable Amazon DevOps Guru for RDS.

Answer

Use RDS Proxy to manage connections.

Answer

Enable RDS Enhanced Monitoring.

Question 5

A database specialist is troubleshooting an Amazon RDS for MySQL DB instance that is running out of storage. The instance has automated backups enabled. The specialist needs to free up storage space immediately without losing backup capability. Which action should the specialist take?

Accepted Answer

Delete older automated backups that are no longer needed.. Option C is correct because deleting old automated backups frees up storage space without affecting the current backup capability. Option A is wrong because modifying the backup retention period does not free space immediately. Option B is wrong because manual snapshots are stored in Amazon S3 and do not affect the DB instance storage. Option D is wrong because disabling backups would stop future backups.

Answer

Modify the DB instance to reduce the backup retention period to 0 days.

Answer

Delete manual snapshots from the RDS console.

Answer

Disable automated backups to stop storage consumption.

Question 6

A database specialist is troubleshooting a slow-running query on an Amazon Aurora MySQL DB cluster. The query performs a large table scan. Which THREE actions would likely improve query performance?

Accepted Answer

Increase the size of the DB instance to provide more memory and CPU.. Creating appropriate indexes can speed up queries by avoiding table scans. Increasing the instance size provides more memory and CPU for query execution. Enabling query caching can store results of repeated queries. Changing isolation level and enabling parallel query may not help in all cases and may have side effects.

Answer

Change the transaction isolation level to SERIALIZABLE.

Answer

Enable Aurora Parallel Query to parallelize the table scan.

Question 7

Refer to the exhibit. A database specialist is troubleshooting an automation script that fails when trying to create a snapshot of the RDS DB instance 'mydb' using an IAM role with the attached policy. The error message indicates that the user is not authorized to perform the operation. Which statement best explains the failure?

Accepted Answer

The policy does not grant the rds:CreateDBSnapshot permission on the DB instance resource.. Option C is correct because the CreateDBSnapshot action requires permissions on both the DB instance and the snapshot resource. The policy only grants access to the snapshot resource, not the DB instance. Options A and B are wrong because the actions are allowed. Option D is wrong because the resource is specified correctly.

Answer

The resource ARN for the snapshot is incorrect; it should specify the DB instance ID.

Answer

The policy does not allow the rds:DescribeDBInstances action on the snapshot resource.

Answer

The policy does not allow the rds:CreateDBSnapshot action on the specific snapshot name.

Question 8

A company is running an Amazon RDS for MySQL database. The application team reports that the database is slow. Upon investigation, you notice that the DB instance's CPU utilization is consistently above 90%. Which initial troubleshooting step should you take?

Accepted Answer

Enable Enhanced Monitoring to identify the source of high CPU usage.. Option B is correct because enabling Enhanced Monitoring provides OS-level metrics that can help identify resource bottlenecks. Option A is wrong because increasing instance size without diagnosis may not address the root cause. Option C is wrong because switching storage type does not reduce CPU load. Option D is wrong because deleting slow query logs removes diagnostic data.

Answer

Increase the DB instance size to improve performance.

Answer

Delete the slow query logs to reduce I/O.

Answer

Change the storage type from General Purpose (gp2) to Provisioned IOPS (io1).

Question 9

A company is using Amazon Redshift for data warehousing. Users report that queries are taking longer than expected. Which CloudWatch metric should be monitored to identify if queries are waiting for resources due to concurrency scaling?

Accepted Answer

ConcurrencyScalingActiveQueries. Option A is correct because ConcurrencyScalingActiveQueries indicates queries running on concurrency scaling clusters. Option B is wrong because WLMQueueLength shows queue wait, not concurrency scaling. Option C is wrong because QueryDuration measures query execution time. Option D is wrong because DiskSpaceUsage is for storage, not concurrency.

Answer

WLMQueueLength

Answer

DiskSpaceUsage

Answer

QueryDuration

Question 10

A company is running an Amazon RDS for Oracle database in Multi-AZ. The primary instance fails over unexpectedly. The DBA wants to determine the cause of the failover. What should the DBA do?

Accepted Answer

View the RDS events in the AWS Management Console.. Option C is correct because RDS events log failover reasons. Option A is wrong because Enhanced Monitoring does not capture failover events. Option B is wrong because CloudTrail logs API calls, not failover reasons. Option D is wrong because error logs may not include failover cause.

Answer

Review the Enhanced Monitoring metrics for the primary instance.

Answer

Query the database error logs for the failover time.

Answer

Check AWS CloudTrail for any database-related API calls.

Question 11

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.

Question 12

A database specialist notices that an RDS MySQL instance's FreeableMemory metric is consistently below 100 MB. Which monitoring tool should be used to identify the queries consuming the most memory?

Accepted Answer

Performance Insights. Option B is correct because Performance Insights shows detailed query-level performance. Option A is wrong because CloudWatch Logs are for log files. Option C is wrong because CloudTrail is for API calls. Option D is wrong because S3 does not monitor RDS memory.

Answer

Amazon S3 access logs

Answer

AWS CloudTrail

Answer

CloudWatch Logs

Question 13

A company uses Amazon ElastiCache for Redis as a caching layer for a web application. They notice increased latency and cache miss rates. The cache cluster has 5 nodes with replication. Which metric should be monitored to identify if the cache is under-provisioned?

Accepted Answer

CPUUtilization. Option A is correct because high CPUUtilization indicates the cache nodes are overloaded. Option B is wrong because CacheHits are a measure of effectiveness, not provisioning. Option C is wrong because Evictions occur when memory is full but CPU is more direct for throughput. Option D is wrong because ReplicationLag indicates replication issues, not capacity.

Answer

ReplicationLag

Answer

CacheHits

Answer

Evictions

Question 14

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The application team reports intermittent connection timeouts. CloudWatch shows increased DatabaseConnections and CPU Utilization during peak hours. Which action should the database specialist take to troubleshoot the issue?

Accepted Answer

Enable slow query log and analyze queries.. Option B is correct because enabling slow query log helps identify long-running queries causing high CPU and connections. Option A is wrong because Multi-AZ failover does not resolve performance issues. Option C is wrong because enhancing CloudWatch metrics does not directly fix timeouts. Option D is wrong because read replicas are for read scaling, not for reducing connection timeouts on the primary.

Answer

Add enhanced monitoring to collect additional metrics.

Answer

Create a read replica and redirect read traffic.

Answer

Failover to the standby instance to refresh connections.

Question 15

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 16

Refer to the exhibit. A database specialist is investigating performance degradation on an Amazon RDS for MySQL DB instance. The BurstBalance metric shows the values above. What does this indicate, and what action should be taken?

Accepted Answer

The instance has exhausted its I/O burst credits; scale up the allocated storage to increase baseline I/O.. Option B is correct because BurstBalance dropping to 0 indicates that the instance has exhausted its I/O burst credits, causing I/O throttling. Scaling up storage to a larger size increases the baseline I/O performance and burst credit earning rate. Option A is wrong because read replicas do not increase I/O credits. Option C is wrong because enabling Performance Insights only helps diagnose, not resolve. Option D is wrong because changing the instance class does not affect I/O credits.

Answer

The instance is experiencing high read load; add a read replica to offload reads.

Answer

The instance's compute capacity is insufficient; change the instance class to a larger size.

Answer

The instance is experiencing a memory bottleneck; enable Performance Insights to analyze query performance.

Question 17

A company's Amazon RDS for PostgreSQL instance is experiencing a high number of connections, causing performance degradation. The DBA wants to identify which user and application are creating the most connections. What should the DBA do?

Accepted Answer

Enable Performance Insights and use the 'db.sql_tokenized' dimension to analyze connections by user.. Option D is correct because Performance Insights with the db.sql_tokenized dimension allows grouping by user and application. Option A is wrong because RDS Enhanced Monitoring does not show SQL-level details. Option B is wrong because VPC Flow Logs capture network traffic, not database connections. Option C is wrong because CloudTrail logs API calls, not database connections.

Answer

Enable AWS CloudTrail to log database logins.

Answer

Enable Enhanced Monitoring and check the 'Connection Count' metric.

Answer

Enable VPC Flow Logs to track connection attempts.

Question 18

A database administrator notices that an Amazon RDS for MySQL DB instance is using more storage than expected. Which metric should be monitored to troubleshoot storage usage?

Accepted Answer

FreeStorageSpace. Option B is correct because FreeStorageSpace indicates remaining capacity. Option A is wrong because DatabaseConnections is about connections. Option C is wrong because ReadIOPS measures I/O operations. Option D is wrong because NetworkThroughput measures network traffic.

Answer

DatabaseConnections

Answer

ReadIOPS

Answer

NetworkThroughput

Question 19

A company is using Amazon ElastiCache for Redis as a caching layer for a web application. Users report that some cached data is missing, causing slower responses. Which ElastiCache feature should be checked first to understand key evictions?

Accepted Answer

Evictions metric in CloudWatch. Option A is correct because Evictions metric shows how many keys are evicted due to memory pressure. Option B is wrong because CacheHits shows hits, not evictions. Option C is wrong because ReplicationLag is for replication. Option D is wrong because CPUUtilization does not directly show evictions.

Answer

ReplicationLag metric

Answer

CPUUtilization metric

Answer

CacheHits metric in CloudWatch

Question 20

A company is using Amazon ElastiCache for Redis and notices that the cache hit ratio is low. The application is frequently reading data that is not in the cache. Which action would be most effective in improving the cache hit ratio?

Accepted Answer

Pre-warm the cache by loading frequently accessed data from the database.. Increasing the cache size may reduce evictions but does not directly improve hit ratio if the working set is not cached. Enabling replication adds replicas but does not increase capacity. Using lazy loading (read-through) and proper cache warming can improve hit ratio. Option A is correct: pre-warming the cache with frequently accessed data can increase the hit ratio.

Answer

Increase the number of replicas in the replication group.

Answer

Decrease the TTL of cached items to ensure freshness.

Answer

Enable Multi-AZ for automatic failover.