DBS-C01 Practice Exam 53 — 20 Questions

Question 1

A company runs a critical application on Amazon RDS for MySQL with Multi-AZ deployment. The application performs frequent writes. The DB instance's CPU utilization is consistently above 80%, and the write latency is high. The company wants to improve write performance without changing the application code. Which solution is MOST effective?

Accepted Answer

Migrate the database to Amazon Aurora MySQL.. Migrating to Amazon Aurora MySQL provides better write performance due to its distributed storage and optimized write path. Option A (increasing instance size) can help but may not be as effective as Aurora; Option C (adding read replicas) does not help write performance; Option D (using Multi-AZ with synchronous replication) already has Multi-AZ, and the latency is due to CPU, not replication.

Answer

Enable Multi-AZ with synchronous replication to a standby instance.

Answer

Add a read replica to offload read traffic.

Answer

Increase the DB instance class to a larger size with more vCPUs.

Question 2

A company runs a critical application on Amazon RDS for PostgreSQL with Multi-AZ. The database has a large table (over 500 GB) that is frequently updated. The operations team notices that the primary instance's CPU usage is consistently above 90%, and the replica lag between the primary and standby is increasing during peak hours. The application can tolerate a few seconds of downtime. The team needs to reduce CPU load and improve write performance without changing the application code. Which action should be taken?

Accepted Answer

Upgrade the DB instance class to a larger size with more vCPUs.. Option A is correct because upgrading to a larger instance class provides more CPU capacity, reducing the load and replication lag. Option B is wrong because read replicas are for read scaling, not for reducing write load on the primary. Option C is wrong because reducing replication lag is not achieved by changing backup retention. Option D is wrong because switching to asynchronous replication is not possible in Multi-AZ and would compromise durability.

Answer

Increase the backup retention period to reduce I/O during backups.

Answer

Modify the DB instance to use asynchronous replication instead of synchronous.

Answer

Create a read replica in the same region and offload read queries to it.

Question 3

A company runs an Amazon RDS for SQL Server DB instance in a VPC. The security group for the DB instance allows inbound traffic on port 1433 from the application servers' security group. The application servers can connect to the database, but a database administrator cannot connect from their workstation using SQL Server Management Studio (SSMS). What is the MOST likely cause?

Accepted Answer

The security group does not allow inbound traffic from the DBA workstation's IP address.. The DBA's workstation is not within the VPC, so it needs a public IP and the security group must allow inbound traffic from the workstation's IP. Option A (DBA's IP not in security group) is correct. Option B (SSMS version) is unlikely; Option C (Multi-AZ) irrelevant; Option D (encryption) does not prevent connection.

Answer

The DBA is using an incompatible version of SSMS.

Answer

The DB instance is configured as Multi-AZ, which restricts direct connections.

Answer

The DB instance has encryption enabled, which blocks non-encrypted connections.

Question 4

A company uses Amazon DynamoDB to store IoT sensor data. Each sensor writes a record every second. The table has a partition key of 'sensor_id' and a sort key of 'timestamp'. Over time, the team notices that write performance degrades for certain sensors that generate more data. The table uses provisioned capacity with auto scaling enabled. The application uses eventual consistency. The team needs to ensure consistent write performance without throttling. Which action should be taken?

Accepted Answer

Modify the partition key to include a random number or prefix to distribute writes evenly.. Option C is correct because adding a random suffix to the partition key distributes writes across partitions, avoiding hot partitions. Option A is wrong because increasing WCU does not solve the partition hot spot, as the limit per partition is fixed. Option B is wrong because switching to on-demand still has per-partition limits. Option D is wrong because a GSI does not change the base table's write distribution.

Answer

Increase the provisioned write capacity units (WCU) to a higher value.

Answer

Switch the table to on-demand capacity mode.

Answer

Create a global secondary index (GSI) with a different partition key to handle writes.

Question 5

A company uses Amazon DynamoDB with global tables in a multi-Region active-active configuration. The application writes to the table in us-east-1 and reads from us-west-2. Recently, a network partition occurred between the two regions, and after recovery, some data was lost. What is the most likely reason for the data loss?

Accepted Answer

The last-writer-wins conflict resolution used timestamp-based coordination without clock synchronization.. Global tables use last-writer-wins (LWW) conflict resolution based on timestamps. If clocks are not synchronized, an older write from one region can overwrite a newer write. Option A (network partition caused inconsistent replication) is not the direct cause; Option B (LWW with unsynchronized clocks) is correct. Option C (Consistent Reads) is unrelated; Option D (TTL) is not relevant.

Answer

The application used eventually consistent reads, causing stale data to be overwritten.

Answer

The table had a TTL attribute that expired the data before replication completed.

Answer

The network partition caused the replication to stop, and data was not replicated.

Question 6

Refer to the exhibit. An IAM policy is attached to a user who needs to manage Amazon RDS DB instances. When the user attempts to modify a DB instance, they receive an 'AccessDenied' error. What is the most likely cause?

Accepted Answer

The policy is missing the 'rds:ListTagsForResource' permission needed for the console.. The policy uses 'ModifyDBInstance' but the correct action is 'ModifyDBInstance' (note: actual action is 'rds:ModifyDBInstance' — but the error could be due to missing 'rds:ModifyDBInstance' for a specific resource if the policy has conditions, but here resource is '*'. However, a common mistake is using 'ModifyDBInstance' instead of 'ModifyDBInstance'? Actually both are correct. The issue might be that the policy does not allow 'rds:ListTagsForResource' which is required for console access. But the question says they receive AccessDenied when modifying. The most plausible answer is that the user is trying to modify a DB instance that has 'DeletionProtection' enabled and the policy does not explicitly allow that action? No. Actually, the error is likely due to the policy missing the 'rds:ModifyDBInstance' action? But it's there. Wait, the exhibit shows 'ModifyDBInstance' which is correct. Hmm. Let me think: The policy allows 'ModifyDBInstance' on all resources, but the user might be using the AWS Management Console which requires additional permissions like 'rds:DescribeDBInstances' (which is present) and 'rds:ListTagsForResource' (not present). So the most likely cause is missing permissions for console-specific actions. Option D mentions 'ListTagsForResource' which is needed for console. So D is correct.

Answer

The policy does not include the 'rds:ModifyDBInstance' action for the specific DB instance ARN.

Answer

The user is trying to modify a Multi-AZ DB instance which requires additional permissions.

Answer

The policy requires a condition to allow modifications during the maintenance window.

Question 7

A database administrator notices that an Amazon RDS for MySQL DB instance has experienced a failover during a maintenance window. What is the most likely cause of this failover?

Accepted Answer

A system update was applied during the maintenance window, causing a reboot. Option C is correct because the RDS maintenance window is used to apply system updates, which may require a reboot and failover if Multi-AZ is enabled. Option A is wrong because manual failover is initiated by the administrator. Option B is wrong because storage scaling does not cause failover. Option D is wrong because read replica creation does not cause failover.

Answer

The DB instance ran out of storage and automatically failed over

Answer

A read replica was promoted to a primary instance

Answer

A manual failover was initiated by the administrator

Question 8

A company runs an Amazon RDS for PostgreSQL DB instance with Multi-AZ enabled. The primary instance is in us-east-1a and the standby is in us-east-1b. During a routine audit, the security team discovers that database connections are being terminated unexpectedly. The database administrator reviews the RDS events and sees an event: 'A Multi-AZ failover has been completed.' What step should be taken to determine the cause of this failover?

Accepted Answer

Review RDS events and AWS CloudTrail logs for API calls related to the failover. Option B is correct because RDS events and CloudTrail logs provide detailed information about failover causes. Option A is wrong because the RDS console shows events but not detailed causes. Option C is wrong because CloudWatch metrics show performance but not failover reasons. Option D is wrong because the RDS API describes instances, not failover causes.

Answer

Examine Amazon CloudWatch metrics for increased CPU or memory usage

Answer

Check the RDS console for maintenance windows

Answer

Run the describe-db-instances CLI command to check the status of the standby

Question 9

A company has an Amazon DynamoDB table with on-demand capacity mode. The table experiences a sudden spike in traffic, and the application starts receiving ProvisionedThroughputExceededException errors. What is the most likely cause?

Accepted Answer

The traffic spike exceeded the previous peak traffic by more than double in a short period. Option D is correct because on-demand mode can throttle if traffic exceeds the previous peak by a large margin in a short time. Option A is wrong because on-demand mode does not have provisioned throughput. Option B is wrong because there is no auto-scaling in on-demand mode. Option C is wrong because read/write capacity units are not set.

Answer

The provisioned read capacity units are insufficient

Answer

The table has reached the maximum number of read capacity units

Answer

Auto Scaling is not configured to increase capacity

Question 10

A company is using Amazon RDS for SQL Server with Multi-AZ and automated backups enabled. The database administrator needs to restore the database to a specific point in time that is within the retention period. What is the correct procedure?

Accepted Answer

Use the RDS console to perform a point-in-time recovery to the desired time. Option B is correct because point-in-time recovery is performed through the RDS console or API by specifying the time. Option A is wrong because it restores the latest backup. Option C is wrong because it restores a manual snapshot. Option D is wrong because automated backups are used for point-in-time recovery.

Answer

Restore from a manual snapshot taken at the desired time

Answer

Use the native SQL Server backup and restore functionality

Answer

Restore from the latest automated snapshot

Question 11

An Amazon RDS for MySQL DB instance has a high number of connections and the application is experiencing slow response times. The database administrator wants to identify the queries that are causing the most load. Which approach is most effective?

Accepted Answer

Enable Amazon RDS Performance Insights and review the top SQL queries. Option C is correct because Performance Insights provides a dashboard to identify top queries by load. Option A is wrong because it shows connections, not query performance. Option B is wrong because CloudWatch logs show slow queries but not in real-time. Option D is wrong because RDS events show instance events, not query load.

Answer

Enable slow query logs and analyze them in CloudWatch Logs

Answer

Monitor the DatabaseConnections metric in CloudWatch

Answer

Check RDS events for any error messages

Question 12

A company is using Amazon DynamoDB with global tables (multi-region) for a gaming application. The application writes to a table in us-east-1 and reads from a table in eu-west-1. The team notices that writes in us-east-1 are taking longer than expected to propagate to eu-west-1. What is the most likely cause?

Accepted Answer

Network latency between the regions is causing replication delay. Option D is correct because global tables eventually replicate asynchronously; network latency between regions can cause delays. Option A is wrong because conflict resolution does not cause delays. Option B is wrong because throughput is separate per region. Option C is wrong because Streams are used for replication, not the cause of delay.

Answer

The write capacity in eu-west-1 is insufficient

Answer

Conflicts are being resolved due to concurrent writes

Answer

DynamoDB Streams is disabled on the table

Question 13

Which TWO actions can be taken to monitor the health of an Amazon DynamoDB table? (Choose 2.)

Accepted Answer

Enable Amazon CloudWatch metrics for the table. Options A and C are correct. CloudWatch metrics provide health indicators (throttling, latency). DynamoDB Streams can be used to track changes but not health directly. Options B and D are incorrect: B is for data plane, D is for monitoring, but not health.

Answer

Use AWS Trusted Advisor to check table limits

Answer

Enable DynamoDB Streams and process events with AWS Lambda

Answer

Use DynamoDB Accelerator (DAX) to improve response times

Question 14

A company is experiencing increased latency on their Amazon RDS for PostgreSQL instance. The application team reports that queries are taking longer than usual. The database metrics show high CPU utilization and a spike in write operations. Which initial step should the database specialist take to diagnose the issue?

Accepted Answer

Enable Performance Insights on the DB instance to analyze the workload.. Enabling Performance Insights provides a detailed performance analysis and helps identify the root cause of the latency. It is the recommended first step for diagnosing database performance issues.

Answer

Create a read replica to offload read traffic from the primary instance.

Answer

Modify the DB instance to a larger instance class to handle the load.

Answer

Enable enhanced monitoring to get OS-level metrics of the DB instance.

Question 15

A database administrator needs to monitor the number of connections to an Amazon RDS for MySQL DB instance. Which Amazon CloudWatch metric should be used?

Accepted Answer

DatabaseConnections. The DatabaseConnections metric in CloudWatch shows the number of current connections to the DB instance.

Answer

NetworkThroughput

Answer

ConnectionAttempts

Answer

ActiveTransactions

Question 16

A company is running an Amazon DynamoDB table with on-demand capacity mode. The table experiences occasional throttling during peak hours. The application team wants to understand the read/write patterns to optimize the table design. Which approach should the database specialist take to analyze the throttling events?

Accepted Answer

Enable CloudWatch Contributor Insights for DynamoDB to identify throttled requests.. CloudWatch Contributor Insights analyzes high-cardinality attributes and provides detailed information about throttling requests, such as which items or partitions are causing throttling.

Answer

Enable DynamoDB Accelerator (DAX) to cache reads and reduce throttling.

Answer

Use AWS CloudTrail to log all DynamoDB API calls and analyze the logs.

Answer

Switch to provisioned capacity mode with auto scaling to handle the spikes.

Question 17

A database administrator is creating an IAM policy to allow a DevOps engineer to manage production RDS instances. The policy above is attached to the engineer's IAM role. The engineer reports that they cannot create a new DB instance with the identifier 'prod-analytics'. What is the most likely reason?

Accepted Answer

The engineer does not have permissions to pass an IAM role to the DB instance if one is specified.. The policy grants permissions to resources matching 'prod-*', but creating a DB instance requires the 'rds:CreateDBInstance' action on the 'arn:aws:rds:us-east-1:123456789012:db:prod-*' resource. However, the CreateDBInstance API call also requires permissions on other resources such as security groups, subnets, etc. But the error is likely because the policy does not allow the action on the specific resource, but the resource ARN matches. Actually, the most common issue is that the policy does not include 'rds:CreateDBInstance' on the 'aws:RequestTag' condition or the resource ARN pattern is incorrect. However, the policy looks correct for the resource. A common mistake is that the policy does not allow 'rds:CreateDBInstance' on the 'arn:aws:rds:us-east-1:123456789012:db:*' for creation, but the policy uses 'prod-*'. That should work. Another possibility is that the engineer is trying to create the instance in a different region or account. But the exhibit shows the policy is for 'us-east-1'. So the most likely reason is that the 'rds:CreateDBInstance' action requires additional permissions on other resources (like EC2 security groups) that are not granted.

Answer

The policy does not allow the 'rds:CreateDBInstance' action on the required resource because the resource ARN pattern is incorrect.

Answer

The policy does not include the 'rds:CreateDBSecurityGroup' action.

Answer

The policy does not include the 'rds:CreateDBInstance' action for all regions.

Question 18

A company is using Amazon Aurora MySQL-Compatible Edition. The database administrator notices that the Aurora cluster has a high number of binary log (binlog) files in the cluster volume, consuming significant storage. The binlog retention period is set to 24 hours. What is the most efficient way to reduce the storage consumed by binlog files without compromising point-in-time recovery (PITR)?

Accepted Answer

Disable binary logging on the Aurora cluster by setting the binlog_format parameter to OFF.. Option D is correct because Aurora MySQL does not rely on binlogs for PITR; it uses its own storage-based recovery. Disabling binlog altogether saves storage and reduces I/O. Option A is incorrect because reducing the retention period may not be sufficient if binlogs are still accumulating. Option B is incorrect because binlog files are not stored on the DB instance but in the cluster volume; deleting them manually is not recommended. Option C is incorrect because using the Binary Log Export feature is for exporting logs, not reducing storage.

Answer

Manually delete binlog files from the DB instance using the 'PURGE BINARY LOGS' command.

Answer

Use the 'Binary Log Export' feature to export binlogs to Amazon S3 and delete them from the cluster.

Answer

Reduce the binlog retention period to 1 hour.

Question 19

Refer to the exhibit. An Amazon RDS for Oracle instance is experiencing ORA-00257 errors. The DBA has already increased the archive log retention setting. What is the most efficient next step to resolve the issue without manual intervention?

Accepted Answer

Modify the DB instance to increase the allocated storage.. Option C is correct. The error indicates the flash recovery area is full. The most efficient automated way is to modify the RDS DB instance to increase allocated storage, which also increases the recovery area. Option A is wrong because manually deleting logs is not automated. Option B is wrong because archiving to S3 is not a standard RDS feature. Option D is wrong because restarting does not free space.

Answer

Configure archiving to Amazon S3 to offload logs.

Answer

Reboot the DB instance to clear the recovery area.

Answer

Manually delete old archive logs from the recovery area using RMAN.

Question 20

Refer to the exhibit. A DBA is checking the backup configuration of an RDS MySQL instance. The current time is 2023-03-15T06:00:00Z. What is the most recent point to which the database can be restored?

Accepted Answer

2023-03-15T04:30:00Z. Option C is correct. The latest restorable time is 2023-03-15T04:30:00Z, which is within the backup window. Option A is wrong because it is after the latest restorable time. Option B is wrong because it is earlier than the latest restorable time. Option D is wrong because the backup window ends at 06:00, but the latest restorable time is 04:30.

Answer

2023-03-15T03:00:00Z

Answer

2023-03-15T05:30:00Z

Answer

2023-03-15T06:00:00Z