DBS-C01 Practice Exam 70 — 20 Questions

Question 1

A company has an Amazon Aurora MySQL DB cluster with a primary instance and two Aurora Replicas. The application is experiencing high write latency. The primary instance's CPU utilization is at 90%, while the replicas are at 30%. The DB cluster parameter group has the default values. Which change is most likely to reduce write latency?

Accepted Answer

Disable the binary log (binlog) on the DB cluster.. High CPU on the primary could be due to the binary log (binlog) being enabled by default for Aurora MySQL. Option B is correct because disabling binlog reduces CPU overhead. Option A is wrong because increasing instance size would help but is not the most likely fix. Option C is wrong because read replicas don't affect write latency. Option D is wrong because increasing storage doesn't reduce CPU.

Answer

Increase the DB instance class of the primary instance.

Answer

Add more Aurora Replicas to distribute the write load.

Answer

Increase the allocated storage of the cluster.

Question 2

A database specialist is troubleshooting an Amazon RDS for SQL Server instance that is running out of storage. The instance has 500 GB of provisioned storage and is using General Purpose SSD (gp2). The specialist wants to set up an alarm to notify when free storage space drops below 50 GB. Which CloudWatch metric and threshold should be used?

Accepted Answer

Monitor the 'FreeStorageSpace' metric in bytes and set a threshold of 53687091200.. Option B is correct because 'FreeStorageSpace' metric in bytes should be monitored. 50 GB = 50 * 1024^3 bytes = 53687091200 bytes. Option A is wrong because 'FreeStorageSpace' in bytes is the correct metric. Option C is wrong because 'FreeStorageSpace' is in bytes, not percent. Option D is wrong because 'FreeStorageSpace' is the correct metric.

Answer

Monitor the 'FreeStorageSpace' metric in percent and set a threshold of 10.

Answer

Monitor the 'DiskSpaceUtilization' metric and set a threshold of 90.

Answer

Monitor the 'FreeStorageSpace' metric in gigabytes and set a threshold of 50.

Question 3

A company is using Amazon DynamoDB for a high-traffic application. Users report occasional 'ProvisionedThroughputExceededException' errors. The application uses consistent reads and retries with exponential backoff. What is the MOST efficient way to handle these errors and reduce the number of retries?

Accepted Answer

Enable DynamoDB Auto Scaling for the table. Option B is correct because DynamoDB Auto Scaling adjusts the provisioned throughput automatically in response to traffic patterns, reducing throttling. Option A is wrong because switching to eventually consistent reads may reduce throttling but changes the consistency model, which may not be acceptable. Option C is wrong because increasing read capacity is a manual action and not efficient. Option D is wrong because increasing write capacity does not address read throttling.

Answer

Increase the provisioned read capacity units manually

Answer

Switch to eventually consistent reads

Answer

Increase the provisioned write capacity units manually

Question 4

A company is using Amazon Redshift and has a query that is running slowly. The DBA wants to identify if the query is I/O-bound. Which TWO metrics from Amazon CloudWatch can indicate I/O-bound queries?

Accepted Answer

ReadIOPS. Options A and D are correct. ReadIOPS measures read operations per second, and ReadLatency measures the time for read operations; both are I/O metrics. WriteIOPS and WriteLatency are also I/O metrics but given the question, the correct ones are ReadIOPS and ReadLatency. Option C is wrong because CPUUtilization indicates CPU-bound, not I/O-bound. Option E is wrong because NetworkReceiveThroughput measures network throughput.

Answer

NetworkReceiveThroughput

Answer

CPUUtilization

Answer

WriteIOPS

Question 5

A company is using Amazon Redshift for data warehousing. The query performance has degraded over time. The DBA suspects that the distribution style of large tables is suboptimal. Which Redshift system view should be queried to identify distribution skew?

Accepted Answer

SVV_DISKUSAGE. Option C is correct because SVV_DISKUSAGE provides information about disk usage per slice, which helps identify skew. Option A is wrong because STL_SCAN is for scan operations. Option B is wrong because STV_TBL_PERM shows permissions. Option D is wrong because PG_TABLE_DEF shows table definitions.

Answer

STL_SCAN

Answer

PG_TABLE_DEF

Answer

STV_TBL_PERM

Question 6

A developer reports that an Amazon ElastiCache for Redis cluster's memory usage is consistently above 90%. The application uses Redis for caching and session storage. Which configuration change would MOST effectively reduce memory pressure?

Accepted Answer

Enable eviction with volatile-LRU policy. Option B is correct because enabling eviction with a volatile-LRU policy frees memory by removing expired keys. Option A is wrong because scaling up increases memory but costs more. Option C is wrong because persistence writes to disk, not memory. Option D is wrong because disabling replication does not reduce memory usage.

Answer

Scale up to a larger node type

Answer

Enable AOF persistence to free memory

Answer

Disable replication to reduce memory overhead

Question 7

A database administrator is monitoring an Amazon RDS for MySQL instance and sees the following CloudWatch metrics: 'DiskQueueDepth' is consistently at 10, 'WriteLatency' is 20 ms, 'FreeStorageSpace' is less than 10% of total. The instance uses gp2 storage. Which THREE actions should be taken to improve performance?

Accepted Answer

Switch to Provisioned IOPS (io1 or io2) for consistent performance. Option A is correct because low free space can cause performance degradation on gp2; increasing storage increases baseline IOPS. Option B is correct because high 'DiskQueueDepth' indicates I/O bottleneck; switching to Provisioned IOPS provides consistent I/O. Option C is correct because enabling Multi-AZ does not improve I/O performance, it adds overhead. Option D is wrong because Performance Insights is a monitoring tool, not a fix. Option E is correct because deleting old data frees up space and can improve performance. So correct: A, B, E.

Answer

Enable Multi-AZ to increase I/O capacity

Answer

Enable Performance Insights to identify slow queries

Question 8

A company is using Amazon RDS for PostgreSQL and needs to monitor the database for performance issues. Which TWO metrics in Amazon CloudWatch are most useful for identifying I/O bottlenecks?

Accepted Answer

ReadIOPS. Option B is correct because ReadIOPS and WriteIOPS show the actual I/O operations. Option D is correct because DiskQueueDepth indicates pending I/O requests, which suggests contention. Option A is wrong because CPU utilization is compute, not I/O. Option C is wrong because FreeStorageSpace is capacity, not performance. Option E is wrong because DatabaseConnections is about connections, not I/O.

Answer

FreeStorageSpace

Answer

DatabaseConnections

Answer

CPUUtilization

Question 9

A developer is troubleshooting an application that uses Amazon DynamoDB. The application sometimes receives ProvisionedThroughputExceededException errors. The table has on-demand capacity mode. The errors occur in short bursts. What is the most likely cause?

Accepted Answer

The request rate exceeds the partition's throughput capacity in a short burst.. On-demand capacity mode can handle up to the table's previous peak traffic. However, if traffic spikes suddenly, DynamoDB might throttle. Option D is correct because on-demand has a limit on the maximum throughput per partition. Option A is wrong because indexes share the table's capacity. Option B is wrong because on-demand does not have provisioned limits. Option C is wrong because the table is on-demand, not provisioned.

Answer

The table has a low read/write capacity mode limit that needs to be increased.

Answer

The global secondary index (GSI) has a different throughput limit.

Answer

The table has reached the maximum provisioned throughput.

Question 10

A company is using Amazon ElastiCache for Redis to cache frequently accessed data. Recently, the application has been experiencing increased latency. The database specialist suspects that the cache hit ratio has decreased. Which CloudWatch metric should the specialist analyze to confirm this suspicion?

Accepted Answer

Monitor 'CacheHits' and 'CacheMisses' metrics to calculate the hit ratio.. Option A is correct because the cache hit ratio is calculated as CacheHits / (CacheHits + CacheMisses). Option B is wrong because CurrConnections shows current connections. Option C is wrong because Evictions shows number of evicted keys. Option D is wrong because ReplicationLag shows replication delay.

Answer

Monitor the 'CurrConnections' metric to see if there are too many connections.

Answer

Monitor the 'Evictions' metric to see if keys are being evicted.

Answer

Monitor the 'ReplicationLag' metric to check replication delay.

Question 11

A database administrator notices that the /var/log/mysql/error.log file on an Amazon RDS for MySQL DB instance is growing rapidly. The administrator wants to monitor the log file size and receive alerts when it exceeds a certain threshold. Which AWS service should be used to set up this monitoring?

Accepted Answer

Amazon CloudWatch Logs. Option D is correct because CloudWatch Logs can monitor log file sizes and trigger alarms based on metric filters. Option A is wrong because CloudTrail does not monitor log file sizes. Option B is wrong because RDS Enhanced Monitoring provides OS-level metrics, not log file metrics. Option C is wrong because S3 is a storage service, not a monitoring service.

Answer

AWS CloudTrail

Answer

Amazon S3

Answer

Amazon RDS Enhanced Monitoring

Question 12

Refer to the exhibit. A DBA is troubleshooting an issue where an IAM user cannot view CloudWatch metrics for an RDS DB instance. The IAM policy attached to the user is shown above. What is the MOST likely reason the user cannot view the metrics?

Accepted Answer

The policy does not include cloudwatch:DescribeAlarms. Option D is correct because the policy is missing the 'rds:DescribeDBInstances' action for the specific DB instance resource, but the issue is about CloudWatch metrics. However, the policy includes 'cloudwatch:GetMetricStatistics' and 'cloudwatch:ListMetrics' with Resource '*', which should allow viewing metrics. But the user cannot view metrics, so the problem might be that the user lacks permission to describe the DB instance to get its identifier. Actually, the question is tricky: the policy allows describing DB instances, so the issue is likely that the user does not have permission to write to CloudWatch Logs? No. The exhibit shows an IAM policy that allows rds:DescribeDBInstances and cloudwatch:GetMetricStatistics and ListMetrics. The user should be able to view metrics. However, the DBA cannot view metrics; the most likely reason is that the policy does not include permission to view CloudWatch alarms or dashboards. But the question says "cannot view CloudWatch metrics", so the policy includes GetMetricStatistics. Option A is wrong because the policy includes that action. Option B is wrong because the resource is '*', so it's not restricted. Option C is wrong because the policy includes rds:DescribeDBInstances. Option D is correct because the user might need additional permissions like cloudwatch:DescribeAlarms or cloudwatch:GetMetricWidgetImage? Actually, the policy seems sufficient for viewing metrics via the console or API. But a common issue is that the console requires additional permissions like cloudwatch:DescribeAlarms for the Metrics page to load. So D is plausible.

Answer

The policy does not include rds:DescribeDBInstances

Answer

The policy uses a Resource element of '*' which is not allowed for CloudWatch

Answer

The policy does not include cloudwatch:GetMetricStatistics

Question 13

An application using Amazon DynamoDB is experiencing higher than expected read costs. The table uses on-demand capacity mode. The read pattern is mostly fetching small items (1 KB) using GetItem. Which of the following is the most cost-effective optimization?

Accepted Answer

Switch to eventually consistent reads for GetItem operations. Option A is correct because DynamoDB charges for read capacity units based on item size, and using GetItem with strongly consistent reads consumes 1 RCU for items up to 4 KB. Option B is wrong because changing to provisioned capacity may not be cost-effective with unpredictable traffic. Option C is wrong because compression is not natively supported. Option D is wrong because DAX adds cost and may not reduce RCU consumption if reads are strongly consistent.

Answer

Change the table to provisioned capacity mode with auto scaling

Answer

Compress the items using application-level compression

Answer

Use DAX to cache the read results

Question 14

A database specialist is monitoring an Amazon DynamoDB global table with two replicas in separate regions. The specialist notices that the 'ReplicatedWriteConflictCount' metric is increasing. What is the MOST likely cause?

Accepted Answer

The same item is being written concurrently in multiple regions. Option D is correct because concurrent writes to the same item in different regions cause conflicts. Option A is wrong because provisioned throughput affects throttling, not conflicts. Option B is wrong because network latency does not cause conflicts. Option C is wrong because eventual consistency does not cause conflicts.

Answer

Insufficient write capacity in one of the regions

Answer

High network latency between the regions

Answer

The application is using strongly consistent reads

Question 15

A company uses Amazon Redshift and notices that queries are taking longer than usual. CloudWatch metrics show 'CPUUtilization' is high and 'DiskSpace' is low. Which TWO actions can help improve query performance?

Accepted Answer

Add more nodes to the cluster. Option A is correct because adding nodes distributes workload and increases CPU and I/O resources. Option B is wrong because VACUUM reorganizes data but does not free space if the disk is full; it may require space. Option C is correct because optimizing sort keys reduces the amount of data scanned, speeding up queries. Option D is wrong because disabling concurrency scaling reduces performance. Option E is wrong because Multi-AZ is not available for Redshift. So correct: A, C.

Answer

Disable concurrency scaling to free resources

Answer

Enable Multi-AZ to distribute load

Answer

Run VACUUM to reclaim space

Question 16

A company's Amazon Aurora MySQL DB cluster is experiencing a failover event. Which THREE metrics in CloudWatch should be examined to understand the cause of the failover?

Accepted Answer

ACUUtilization. Option A is correct because FailoverCount shows how many failovers occurred. Option B is correct because DatabaseConnections can indicate if connections were dropped or maxed out. Option D is correct because ACUUtilization can show resource exhaustion that may trigger failover. Option C is wrong because BinLogDiskUsage is about binary logs, not failover cause. Option E is wrong because ReadLatency is a symptom but not a direct cause of failover.

Answer

ReadLatency

Answer

BinLogDiskUsage

Question 17

A company runs an Amazon RDS for Oracle DB instance. The database administrator wants to receive an alert when the storage space is below 10% of the allocated storage. Which Amazon CloudWatch metric and alarm threshold should be used?

Accepted Answer

Metric: FreeStorageSpace, Condition: < 10% of 100 GB (10 GB). The metric FreeStorageSpace shows the available storage in bytes. The alarm should be set to when FreeStorageSpace is less than 10% of allocated storage. Option B is correct. Option A is wrong because it's a percentage of total. Option C is wrong because it's a fixed value. Option D is wrong because BinaryLog usage is not relevant.

Answer

Metric: BinaryLogUsage, Condition: > 10%

Answer

Metric: FreeableMemory, Condition: < 10% of total memory

Answer

Metric: DiskQueueDepth, Condition: > 10

Question 18

A database specialist is trying to connect to an Amazon RDS for MySQL instance from an EC2 instance but receives a 'Connection timed out' error. The security group for the RDS instance allows inbound traffic on port 3306 from the security group of the EC2 instance. What should the specialist check next?

Accepted Answer

Check the network ACL associated with the subnet of the RDS instance to ensure it allows inbound traffic on port 3306 and outbound traffic on ephemeral ports.. Option D is correct because the network ACL must allow inbound traffic on ephemeral ports for the response. Option A is wrong because the security group already allows inbound on 3306. Option B is wrong because the error is 'Connection timed out', not authentication. Option C is wrong because if the VPC had no internet gateway, the error would be different for private connections.

Answer

Check that the RDS instance has a public DNS name and the EC2 instance can resolve it.

Answer

Ensure that the VPC has an internet gateway attached and the route table has a route to it.

Answer

Verify that the security group for the EC2 instance allows outbound traffic on port 3306.

Question 19

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database uses Oracle Data Guard for disaster recovery. Which AWS service should be used to monitor the replication lag between the source and target databases during migration?

Accepted Answer

AWS Database Migration Service (AWS DMS). Option B is correct because AWS DMS provides metrics for replication lag. Option A is wrong because CloudWatch can monitor DMS metrics but is not specific to Data Guard. Option C is wrong because RDS Performance Insights does not monitor replication lag. Option D is wrong because CloudTrail does not monitor replication lag.

Answer

Amazon RDS Performance Insights

Answer

Amazon CloudWatch

Answer

AWS CloudTrail

Question 20

Refer to the exhibit. A DBA sees the above error log entries for an Amazon RDS for MySQL DB instance. Which action should the DBA take to resolve the 'Too many connections' error?

Accepted Answer

Modify the DB parameter group to increase max_connections. Option B is correct because increasing the max_connections parameter allows more concurrent connections. Option A is wrong because rebooting does not increase the connection limit. Option C is wrong because modifying the security group does not affect database connections. Option D is wrong because the error is not about authentication.

Answer

Reboot the DB instance

Answer

Modify the DB security group to allow more connections

Answer

Reset the DB instance master user password