DBS-C01 Practice Exam 63 — 20 Questions

Question 1

Refer to the exhibit. A database specialist is investigating an application outage that occurred at 14:25 UTC. The RDS event log shows the events above. What is the most likely cause of the outage?

Accepted Answer

A Multi-AZ failover occurred at 14:25 UTC, causing a brief outage.. Option A is correct because a Multi-AZ failover can cause a brief outage during the transition. The restart at 14:30 is likely the result of the failover. Option B is wrong because the restart occurred after the failover. Option C is wrong because the events do not indicate a maintenance window. Option D is wrong because there is no evidence of insufficient storage.

Answer

A maintenance window update was applied, causing the instance to become unavailable.

Answer

The DB instance ran out of storage and became read-only.

Answer

The DB instance restarted at 14:30 UTC due to a manual reboot.

Question 2

A company has an Amazon DynamoDB table with auto scaling enabled. During a traffic spike, the application experiences high write latencies. Which action should the company take to troubleshoot the latency issue?

Accepted Answer

Monitor the ThrottledWriteEvents metric in CloudWatch.. Option B is correct because CloudWatch metrics for ThrottledWriteEvents help identify if auto scaling is keeping up. Option A is wrong because disabling auto scaling may cause throttling. Option C is wrong because changing to on-demand may not be cost-effective and is not a troubleshooting step. Option D is wrong because increasing read capacity does not affect write latency.

Answer

Switch the table to on-demand capacity mode.

Answer

Disable auto scaling and manually increase write capacity.

Answer

Increase the read capacity of the table.

Question 3

Which TWO metrics should be monitored to troubleshoot an Amazon RDS for PostgreSQL database that is experiencing high connection count and connection timeouts?

Accepted Answer

DatabaseConnections. Options B and D are correct. DatabaseConnections shows current connections, and BurstBalance helps understand if I/O is throttled. Option A is wrong because SwapUsage is not a standard RDS metric. Option C is wrong because ReadLatency is about I/O latency, not connections. Option E is wrong because NetworkTransmitThroughput is about network, not connections.

Answer

NetworkTransmitThroughput

Answer

SwapUsage

Answer

ReadLatency

Question 4

A company's RDS for SQL Server instance is frequently running out of disk space. The instance uses General Purpose SSD (gp2) storage. Which monitoring step will help identify the root cause?

Accepted Answer

Monitor FreeStorageSpace and BinaryLogUsage metrics. Option D is correct because monitoring FreeStorageSpace and transaction log usage reveals what consumes space. Option A is wrong because backup storage is separate. Option B is wrong because Enhanced Monitoring shows OS metrics, not disk usage by database. Option C is wrong because CloudTrail is for API activity.

Answer

Review CloudTrail logs for API calls

Answer

Monitor BackupStorageUsed metric

Answer

Enable Enhanced Monitoring

Question 5

A company's DynamoDB table uses provisioned capacity and has a global table for disaster recovery. Write requests to the replica region are failing with ProvisionedThroughputExceededException even though the replica table shows low consumed capacity. What is the MOST likely cause?

Accepted Answer

The replica table's write capacity is insufficient for replication writes. Option D is correct because replicas have independent capacity; if replication writes exceed provisioned capacity, throttling occurs. Option A is wrong because burst capacity is not relevant to throttling. Option B is wrong because auto-scaling doesn't cause throttling. Option C is wrong because DAX is for reads.

Answer

Auto-scaling is disabled on the replica table

Answer

The replica table is exhausting its burst capacity

Answer

DAX is enabled on the replica table

Question 6

A company runs an Amazon RDS for PostgreSQL instance with Multi-AZ deployment. The primary DB instance fails unexpectedly and a failover occurs. Which action should be taken to minimize downtime during future failovers?

Accepted Answer

Enable Multi-AZ deployment to automatically failover to the standby.. Using a read replica as a failover target is not supported in RDS for PostgreSQL. Multi-AZ already provides automatic failover; no additional action is needed. Option B is correct: Multi-AZ automatically handles failover.

Answer

Configure an Amazon RDS Proxy to reduce failover time.

Answer

Increase the DB instance size to reduce failover time.

Answer

Create a read replica in the same region and promote it during failover.

Question 7

A database team is troubleshooting a performance issue on an Amazon RDS for PostgreSQL instance. They notice that the 'DiskQueueDepth' metric is consistently high. Which TWO actions should the team take to resolve this issue? (Choose TWO.)

Accepted Answer

Enable storage auto scaling.. Options B and D are correct. A high disk queue depth indicates I/O bottleneck. Increasing IOPS (Option B) or enabling Auto Scaling (Option D) can alleviate the bottleneck. Option A is wrong because more connections may increase I/O contention. Option C is wrong because query caching is not a primary solution for I/O. Option E is wrong because Multi-AZ does not improve I/O performance.

Answer

Increase the number of database connections.

Answer

Enable query caching in PostgreSQL.

Answer

Enable Multi-AZ deployment.

Question 8

A company is experiencing increased latency on their RDS for PostgreSQL instance. The CloudWatch metrics show high ReadIOPS but low CPU utilization. Which action is MOST likely to resolve the issue?

Accepted Answer

Increase the instance size or switch to a gp3 volume. Option C is correct because increasing the instance size or switching to a storage-optimized instance reduces I/O latency. Option A is wrong because Aurora is not the same as PostgreSQL. Option B is wrong because Multi-AZ does not improve performance. Option D is wrong because enabling auto-scaling only scales storage, not performance.

Answer

Migrate the database to Amazon Aurora PostgreSQL

Answer

Enable Multi-AZ deployment

Answer

Enable storage auto-scaling

Question 9

Which TWO settings should be verified when troubleshooting an RDS for MySQL instance that has a high number of aborted connections? (Choose 2.)

Accepted Answer

connect_timeout parameter. Options A and C are correct because connection timeout and max allowed packet can cause aborted connections. Option B is wrong because max_connections limits total connections but not aborts. Option D is wrong because query cache is not related to connections. Option E is wrong because binlog retention is for replication.

Answer

query_cache_type parameter

Answer

binlog_retention_hours parameter

Answer

max_connections parameter

Question 10

An Amazon RDS for MySQL instance is running out of storage. Which TWO actions can be taken to resolve this issue without downtime?

Accepted Answer

Enable storage auto scaling to automatically add storage.. RDS supports modifying storage to increase allocated storage without downtime. You can also enable storage auto scaling to automatically increase storage. Option C (deleting data) may free space but is not recommended as a proactive measure. Option D (snapshot and restore) involves downtime. Option E (conversion to Aurora) is a migration, not a direct fix.

Answer

Delete unnecessary data from the instance.

Answer

Take a snapshot and restore to a larger instance.

Answer

Convert the instance to Amazon Aurora.

Question 11

A gaming company uses Amazon DynamoDB with provisioned capacity. During a new game launch, the read activity spikes and some requests receive 'ProvisionedThroughputExceededException' errors. The operations team needs to monitor read throttling in real-time. Which CloudWatch metric should they create an alarm for?

Accepted Answer

ReadThrottleEvents. Option B is correct because ReadThrottleEvents directly measures throttled read requests. Option A is wrong because ConsumedReadCapacityUnits shows actual usage, not throttled events. Option C is wrong because ThrottledRequests includes write throttles as well. Option D is wrong because ReadLatency shows latency, not throttling.

Answer

ReadLatency

Answer

ConsumedReadCapacityUnits

Answer

ThrottledRequests

Question 12

A company is running an Amazon DocumentDB cluster. The application is experiencing high write latency. The cluster has a single instance. What should be done to identify the cause of the latency?

Accepted Answer

Enable Performance Insights and review the top wait events.. Option A is correct because enabling Performance Insights helps identify slow queries. Option B is wrong because adding a replica does not diagnose latency. Option C is wrong because increasing instance size is a reactive step. Option D is wrong because changing storage type may not address latency.

Answer

Upgrade the instance to a larger size.

Answer

Add a replica to distribute the write load.

Answer

Change the storage type to Provisioned IOPS.

Question 13

A team is troubleshooting a DynamoDB table that has high read latency. The table uses on-demand capacity and has a global secondary index (GSI). Which configuration is MOST likely causing the issue?

Accepted Answer

The GSI has provisioned capacity set too low. Option A is correct because an under-provisioned GSI can throttle reads even if the base table uses on-demand. Option B is wrong because on-demand handles bursts. Option C is wrong because TTL does not affect read latency. Option D is wrong because DynamoDB Accelerator (DAX) reduces latency, not increases.

Answer

Time-to-Live (TTL) is enabled

Answer

DAX is enabled for the table

Answer

The table uses on-demand capacity

Question 14

A database administrator wants to receive an alert when an RDS instance's storage space drops below 10% of total allocated storage. Which AWS service should be used to set up this alert?

Accepted Answer

Amazon CloudWatch Alarms. Option B is correct because CloudWatch Alarms can trigger on FreeStorageSpace metric. Option A is wrong because SNS is a notification service, not monitor. Option C is wrong because CloudTrail is for API activity. Option D is wrong because Config tracks configuration changes.

Answer

Amazon SNS

Answer

AWS CloudTrail

Answer

AWS Config

Question 15

A developer reports that an Amazon RDS for MySQL DB instance is experiencing high CPU utilization. You suspect a specific query is causing the issue. Which CloudWatch metric should you examine to confirm this?

Accepted Answer

CPUUtilization. The 'CPUUtilization' metric directly measures CPU usage. Options A, B, and D are not metrics that indicate CPU usage.

Answer

DatabaseConnections

Answer

ReadLatency

Answer

FreeableMemory

Question 16

A developer is troubleshooting an application that writes to an Amazon ElastiCache for Redis cluster. The application occasionally fails with 'OOM command not allowed when used memory > maxmemory'. What is the most likely cause?

Accepted Answer

The cluster's maxmemory-policy is set to noeviction.. Option C is correct because this error indicates the cache has reached its memory limit and eviction policy is not set or set to noeviction. Option A is wrong because that error is about keyspace notifications. Option B is wrong because cluster mode may affect sharding but not this specific error. Option D is wrong because connection limit would show a different error.

Answer

The cluster's maxclients limit has been reached.

Answer

The cluster has too many keyspace notifications enabled.

Answer

The cluster is in cluster mode and cross-slot commands are used.

Question 17

A developer reports that an application's write requests to a DynamoDB table are failing with ProvisionedThroughputExceededException. The table uses provisioned capacity. Which immediate action will resolve the issue?

Accepted Answer

Implement exponential backoff in the application. Option C is correct because implementing exponential backoff reduces request rate temporarily. Option A is wrong because switching to on-demand takes 30 minutes. Option B is wrong because deleting GSI does not help writes to main table. Option D is wrong because DAX caches reads, not writes.

Answer

Switch the table to on-demand capacity

Answer

Enable DynamoDB Accelerator (DAX)

Answer

Delete all global secondary indexes

Question 18

Which TWO metrics should be monitored to detect a memory leak in an RDS for Oracle instance? (Choose 2.)

Accepted Answer

SwapUsage. Options A and D are correct because FreeableMemory shows available memory, and SwapUsage indicates when the OS uses swap due to memory pressure, both signs of a memory leak. Option B is wrong because DatabaseConnections does not directly indicate memory leak. Option C is wrong because ReadIOPS relates to I/O, not memory. Option E is wrong because CPUUtilization may be high but not specific to memory leak.

Answer

DatabaseConnections

Answer

CPUUtilization

Answer

ReadIOPS

Question 19

A team is troubleshooting an Amazon DynamoDB table that is throttling write requests. The table has on-demand capacity mode enabled. Which of the following is the most likely cause of the throttling?

Accepted Answer

The write traffic exceeds the table's previous peak traffic by more than double.. Even with on-demand capacity, DynamoDB can throttle if you exceed the account-level provisioned throughput limits or if there is a sudden spike that exceeds the previous peak traffic by a large margin. Option C is correct; Option A is incorrect because on-demand does not have per-table limits. Option B is incorrect because adaptive capacity helps but does not prevent all throttling. Option D is a possible reason but not the most likely.

Answer

The table has exceeded its provisioned write capacity units.

Answer

The table is not using adaptive capacity.

Answer

There is an active AWS Health event affecting the DynamoDB service.

Question 20

A company has an Amazon Aurora MySQL DB cluster with one writer and two readers. The application is reporting increased read latency. The DB cluster is using Aurora Auto Scaling for readers. Which metric should be used to trigger scaling out readers?

Accepted Answer

AverageActiveConnections. Aurora Auto Scaling for readers uses the 'AverageActiveConnections' metric to determine when to add readers. Option B is correct. Option A is incorrect because the auto scaling is based on connections, not CPU. Option C is incorrect because ReaderNodeCPU is not a predefined metric for auto scaling. Option D is incorrect because ReadLatency is an effect, not a scaling trigger.

Answer

ReadLatency

Answer

ReaderNodeCPU

Answer

CPUUtilization