DBS-C01 Practice Exam 59 — 20 Questions

Question 1

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The primary instance recently experienced an unexpected failover due to a hardware failure. The database is 2 TB in size and has high write throughput. Which TWO actions should the database administrator take to minimize recovery time and ensure data durability?

Accepted Answer

Enable automated backups with a retention period of 1 day to allow point-in-time recovery.. Option B is correct because enabling automated backups with a short retention period ensures point-in-time recovery. Option D is correct because verifying that the Multi-AZ failover completed successfully confirms data consistency. Option A is wrong because increasing instance size may not directly improve failover time. Option C is wrong because disabling Multi-AZ reduces availability. Option E is wrong because manual snapshots are not as immediate as automated backups for recovery.

Answer

Increase the DB instance class to a larger size to handle the write load.

Answer

Disable Multi-AZ and use a single-AZ deployment to avoid future failovers.

Answer

Take a manual snapshot of the DB instance immediately.

Question 2

A company runs an Amazon Aurora MySQL database. The database experiences a sudden spike in connections and then becomes unresponsive. The DB instance has a db.r5.large class with 8 GB memory. The maximum connections parameter is set to the default. Which is the most likely cause of the unresponsiveness?

Accepted Answer

The number of connections exceeded the max_connections limit. Option C is correct because the default max_connections for Aurora MySQL is based on memory, and with 8 GB, it is about 800. A spike exceeding that can exhaust resources. Option A is wrong because storage auto-scaling is seamless. Option B is wrong because burst balance applies to gp2 volumes, but Aurora uses cluster storage. Option D is wrong because replica lag would affect reads, not make the instance unresponsive.

Answer

The DB instance's EBS burst balance dropped to zero

Answer

The storage volume ran out of allocated space

Answer

A read replica had high replication lag

Question 3

A database administrator needs to monitor Amazon RDS for PostgreSQL connections and terminate idle connections that have been open for more than 1 hour. Which combination of steps should be taken?

Accepted Answer

Enable audit logging and stream to Amazon CloudWatch Logs. Create a metric filter for connection events. Use CloudWatch Alarm to trigger a Lambda function that runs a SQL query to terminate idle connections.. CloudWatch Logs capture connection logs. Lambda can query the database to terminate idle connections. Option A is correct. Option B uses EC2 which is less automated. Option C uses RDS Event Notifications which do not include connection details. Option D lacks Lambda automation.

Answer

Use Amazon RDS Performance Insights to view active connections and manually terminate idle connections via the AWS Management Console.

Answer

Configure an RDS event subscription for 'connection' events and send to Amazon SNS. Use SNS to notify an EC2 instance that runs a script to terminate idle connections.

Answer

Enable RDS Enhanced Monitoring and configure a CloudWatch alarm to invoke an AWS Lambda function that terminates idle connections.

Question 4

A multinational e-commerce company runs an Amazon Aurora MySQL database for its product catalog. The database is 2 TB and has a high write volume. The company needs to create a test environment that contains a subset (10%) of the production data for developers to use. The test environment must be refreshed daily with the latest production data. The operations team wants to minimize cost and ensure that the test environment does not impact production performance. Which solution should they implement?

Accepted Answer

Use Aurora cloning to create a clone of the production cluster. Use database triggers or scripts to delete 90% of the data after cloning.. Using Aurora cloning creates a copy that shares storage with the source, minimizing cost and avoiding performance impact. Option A is correct. Option B (snapshot and restore) creates a full copy, costing more. Option C (DMS) adds cost and overhead. Option D (read replica and promote) would impact production replication.

Answer

Use AWS DMS to continuously replicate a filtered subset of data to a test cluster.

Answer

Take a manual snapshot of the production cluster, restore it to a new cluster, and delete 90% of the data.

Answer

Create a read replica of the production cluster, promote it to a standalone cluster, and delete 90% of the data.

Question 5

A company uses Amazon DynamoDB with auto scaling enabled. During a flash sale, write traffic spikes and some requests receive ThrottlingException errors. The table's write capacity auto scaling reaches the maximum configured capacity but still throttles. Which TWO actions should resolve the throttling? (Choose TWO.)

Accepted Answer

Increase the maximum write capacity setting for the auto scaling policy.. Option A increases maximum capacity to allow auto scaling to scale higher. Option C improves partition key distribution to avoid hot partitions. Option B does not help because auto scaling already reached max. Option D is not a DynamoDB feature. Option E is irrelevant.

Answer

Add a DynamoDB Accelerator (DAX) cluster to cache writes.

Answer

Enable DynamoDB Streams to offload write traffic.

Answer

Disable auto scaling and use On-Demand capacity mode.

Question 6

A database administrator is reviewing the configuration of an RDS MySQL instance. Based on the exhibit, which change would MOST improve the database's performance under heavy write workloads without increasing costs significantly?

Accepted Answer

Change the storage type from gp2 to gp3 to get higher baseline IOPS and throughput.. Option B is correct because gp2 volumes have performance limits based on size; upgrading to gp3 provides better baseline performance and IOPS scaling. Option A is wrong because Multi-AZ is already enabled. Option C is wrong because default parameter groups are not optimized; custom groups can improve performance. Option D is wrong because increasing backup retention period does not improve performance.

Answer

Change the DB parameter group to a custom one with optimized MySQL parameters.

Answer

Increase the backup retention period to 35 days to improve performance.

Answer

Enable Multi-AZ to improve write performance.

Question 7

A company is running an Amazon RDS for MySQL Multi-AZ DB instance. The application experiences a brief write disruption during automatic failover. The database workload has low write latency requirements. Which configuration change would minimize application impact during failover?

Accepted Answer

Change the DB instance to use a Multi-AZ DB cluster configuration.. Using a read replica for failover is not supported in RDS MySQL; Multi-AZ is the correct approach. Option D (Multi-AZ cluster) provides faster failover than Multi-AZ with a standby. Option A is correct because RDS Multi-AZ cluster uses a writer and two reader instances, reducing failover time. Option B is not supported. Option C increases cost without performance benefit.

Answer

Create a read replica in a different Availability Zone and promote it during failover.

Answer

Use a single-AZ deployment and rely on automated backups for recovery.

Answer

Increase the DB instance class to reduce failover time.

Question 8

A developer is troubleshooting an application that is unable to write to a DynamoDB table. The above IAM policy is attached to the IAM role used by the application. What is the likely cause?

Accepted Answer

The Deny statement overrides the Allow statement, blocking all DynamoDB actions.. Option B is correct because the Deny statement for all DynamoDB actions overrides the Allow for PutItem. Deny statements always take precedence. Option A is wrong because the table name is correct. Option C is wrong because the role is assumed. Option D is wrong because the user exists.

Answer

The table name in the Resource ARN is incorrect.

Answer

The IAM user does not exist.

Answer

The role is not correctly assumed by the application.

Question 9

A development team is using Amazon RDS for MySQL with read replicas to offload reporting queries. They notice that the read replica is consistently lagging behind the primary by several seconds. The primary handles 5000 writes per second. Which action would most likely reduce replica lag?

Accepted Answer

Increase the instance size of the read replica.. Option D is correct because increasing the replica instance size can improve its ability to apply changes faster. Option A is incorrect because disabling binary logging would break replication. Option B is incorrect because the replica lag is due to the replica not keeping up, not the primary. Option C is incorrect because Multi-AZ is for high availability, not for reducing replica lag.

Answer

Increase the 'max_connections' parameter on the primary instance.

Answer

Disable binary logging on the primary instance to reduce I/O.

Answer

Convert the primary instance to a Multi-AZ deployment.

Question 10

A company uses Amazon DynamoDB with global tables. They notice that changes made in one region are not appearing in another region after several minutes. Which CloudWatch metric should be monitored to check the replication lag?

Accepted Answer

ReplicationLatency. Option C is correct because ReplicationLatency measures the time between the last update on the source table and the last update on the replica table. Option A is wrong because ThrottledRequests indicates throttling. Option B is wrong because ConsumedWriteCapacityUnits measures usage. Option D is wrong because SuccessfulRequestLatency measures request latency.

Answer

ConsumedWriteCapacityUnits

Answer

SuccessfulRequestLatency

Answer

ThrottledRequests

Question 11

A company is running an Amazon RDS for MySQL Multi-AZ DB instance. They notice that the application is experiencing increased latency during peak hours. The DB instance's CPU utilization is consistently above 80%, and the Read Latency metric is high. Which action would most effectively reduce the latency without requiring application changes?

Accepted Answer

Create a read replica and direct read queries to it.. Option D is correct because Multi-AZ deployments with read replicas offload read traffic and reduce latency. Option A is wrong because increasing instance size may help but does not specifically address read latency. Option B is wrong because enabling Multi-AZ alone does not reduce read latency. Option C is wrong because disabling Multi-AZ would remove the standby, reducing availability.

Answer

Disable Multi-AZ to free up resources.

Answer

Increase the DB instance class to a larger size.

Answer

Enable Multi-AZ on the DB instance.

Question 12

A company runs an Amazon Aurora MySQL database cluster with one writer and two readers. The application suddenly fails with 'Too many connections' error. The writer instance's maximum connections is set to 1000. Which configuration change would best resolve the issue while maintaining high availability?

Accepted Answer

Enable Amazon RDS Proxy for the database cluster.. Option D is correct because a multi-threaded application may exhaust connections; using a connection pooler like RDS Proxy reduces connection churn. Option A is wrong because increasing max_connections may overload the instance. Option B is wrong because read replicas do not accept writes. Option C is wrong because it's not a configuration change.

Answer

Increase the max_connections parameter on the writer instance to 5000.

Answer

Redirect all write requests to one of the read replicas.

Answer

Manually kill idle connections from the database.

Question 13

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 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 DynamoDB for a session management application. The application is experiencing higher latency during peak hours. The DynamoDB table uses on-demand capacity. Which TWO steps should a database specialist take to diagnose the issue?

Accepted Answer

Check the CloudWatch metric for ThrottledRequests to see if any requests are being throttled.. Checking ThrottledRequests helps identify if requests are being throttled, even with on-demand. Reviewing PartitionKey metrics helps detect hot partitions. ReadCapacityUnits and WriteCapacityUnits are not applicable for on-demand. Latency metrics show end-to-end performance but are less diagnostic.

Answer

Review the table's ReadCapacityUnits and WriteCapacityUnits to ensure they are sufficient.

Answer

Examine the CloudWatch metric for UserErrors to identify client-side issues.

Answer

Enable DynamoDB Streams to capture all write events for analysis.

Question 16

A developer is troubleshooting an application that uses Amazon DynamoDB. The application is experiencing throttled requests (ProvisionedThroughputExceededException). Which CloudWatch metric should be monitored to troubleshoot this issue?

Accepted Answer

ConsumedWriteCapacityUnits. Option C is correct because ConsumedWriteCapacityUnits shows actual usage; comparing with ProvisionedWriteCapacityUnits helps identify throttling. Option A is wrong because UserErrors is for client-side errors. Option B is wrong because ThrottledRequests is a metric but not a CloudWatch metric name; the actual metric is ConsumedWriteCapacityUnits. Option D is wrong because SuccessfulRequestLatency is about latency, not throttling.

Answer

ThrottledRequests

Answer

SuccessfulRequestLatency

Answer

UserErrors

Question 17

A company is using Amazon ElastiCache for Redis as a caching layer. The application performance degrades when cache misses increase. Which metric should be monitored to track the cache hit rate?

Accepted Answer

CacheHits and CacheMisses. Option D is correct because CacheHits and CacheMisses together give the hit rate. Option A is wrong because CPUUtilization is for resource usage. Option B is wrong because Evictions indicates memory pressure, not hit rate. Option C is wrong because CurrConnections shows active connections.

Answer

CurrConnections

Answer

CPUUtilization

Answer

Evictions

Question 18

Which TWO CloudWatch metrics should be monitored to determine if an Amazon Aurora MySQL DB cluster has sufficient I/O capacity?

Accepted Answer

ReadIOPS. Options B and D are correct. ReadIOPS and WriteIOPS show actual I/O operations. Option A is wrong because CPUUtilization is about CPU. Option C is wrong because DatabaseConnections is about connections. Option E is wrong because FreeableMemory is about memory.

Answer

FreeableMemory

Answer

CPUUtilization

Answer

DatabaseConnections

Question 19

A developer executed a DELETE statement without a WHERE clause on an Amazon RDS for PostgreSQL instance. The transaction is still open. Which action should the developer take to undo the DELETE without affecting other operations?

Accepted Answer

Execute ROLLBACK in the same session.. Option A is correct because an open transaction can be rolled back using the ROLLBACK command. Option B is incorrect because Point-in-Time Recovery restores the entire DB instance to a previous timestamp, not just the transaction. Option C is incorrect because ROLLBACK will undo the DELETE. Option D is incorrect because COMMIT would make the DELETE permanent.

Answer

Execute COMMIT and then run a recovery script.

Answer

Use the Point-in-Time Recovery feature to restore the database to a time before the DELETE.

Answer

Stop the DB instance and restore from the latest snapshot.

Question 20

A developer is troubleshooting a slow-running query on an Amazon RDS for PostgreSQL instance. The query is performing a sequential scan on a large table. Which AWS service or feature should the developer use to identify the missing index?

Accepted Answer

Amazon RDS Performance Insights. Option B is correct because Performance Insights provides database performance analysis and can identify missing indexes. Option A is wrong because RDS Enhanced Monitoring provides OS-level metrics. Option C is wrong because CloudWatch Logs are for application logs. Option D is wrong because AWS CloudTrail logs API calls.

Answer

Amazon RDS Enhanced Monitoring

Answer

AWS CloudTrail

Answer

Amazon CloudWatch Logs