DBS-C01 Management and Operations — Timed 15 Questions

Question 1

A company runs a production Amazon RDS for PostgreSQL DB instance. The database experiences intermittent high latency during peak hours. The company's monitoring shows that CPU utilization is below 40%, memory is adequate, and network throughput is normal. The DB instance uses General Purpose SSD (gp2) storage with 3,000 Provisioned IOPS. Which TWO actions should a database specialist take to diagnose and resolve the performance issue? (Choose two.)

15 minute time limit — choose an answer to begin.

Accepted Answer

Check the Burst Balance metric in Amazon CloudWatch for the DB instance.. Gp2 storage uses a credit-based burst model, and the Burst Balance metric indicates the remaining I/O credits. If the burst balance is depleted, the instance is throttled to the baseline IOPS (3,000 for this size), causing high latency despite low CPU and adequate memory. Option E is also correct because monitoring Read/Write Latency metrics in CloudWatch directly measures storage performance and can confirm whether high latency is due to storage I/O issues. Together, these two metrics help identify if the gp2 burst credits are exhausted or if other storage-related latencies are occurring. Options B, C, and D are not the most appropriate first diagnostic steps: B suggests changing storage type without diagnosis, C does not directly address storage I/O, and D checks memory pressure, which is not indicated given adequate memory.

Answer

Change the storage type to Provisioned IOPS SSD (io1) with 10,000 IOPS.

Answer

Increase the Read IOPS by modifying the instance to a larger instance class.

Answer

Review the SwapUsage metric for the DB instance to check for memory pressure.

Question 2

Which TWO actions can help reduce the recovery time objective (RTO) for an Amazon RDS for PostgreSQL DB instance in the event of a failure? (Choose 2.)

Accepted Answer

Enable Multi-AZ deployment.. Enabling Multi-AZ deployment for Amazon RDS for PostgreSQL provides automatic failover to a standby replica in a different Availability Zone. This reduces RTO by automating the DNS change and database promotion, typically completing within 60–120 seconds without manual intervention. Option C is correct because creating a read replica in a different Availability Zone allows you to manually promote it to a standalone instance during a failure, which can be faster than restoring from a backup, thereby reducing RTO. Although promotion is manual and takes a few minutes, it still offers a lower RTO compared to backup-based recovery. Option D, configuring automated backups with point-in-time recovery, primarily improves recovery point objective (RPO) rather than RTO, as restoring from a backup is typically slower and involves more steps. Options A and E do not directly reduce RTO since increasing instance class size does not aid failover, and manual snapshots also rely on restoration.

Answer

Increase the DB instance class size.

Answer

Configure automated backups with point-in-time recovery.

Answer

Take manual snapshots every hour.

Question 3

A company's Amazon RDS for MySQL instance is experiencing high CPU utilization. The company's application is write-heavy. The database administrator wants to reduce the load on the primary instance. Which solution is MOST effective?

Accepted Answer

Increase the instance size of the RDS instance.. Increasing the instance size (Option A) provides more CPU and IO capacity to handle the write-heavy workload, thereby reducing CPU utilization. Read replicas (B) can offload read traffic but not write load. Multi-AZ (C) enhances availability but does not distribute writes; writes continue on the primary. ElastiCache (D) caches reads, not writes, so it does not reduce write-related CPU load.

Answer

Create a read replica and redirect read traffic to it.

Answer

Enable Multi-AZ deployment to distribute writes.

Answer

Use Amazon ElastiCache to cache frequent writes.

Question 4

A company wants to monitor the performance of an Amazon RDS for MySQL instance. Which TWO metrics are available in Amazon CloudWatch by default? (Choose 2.)

Accepted Answer

FreeableMemory. CPUUtilization (Option B) and FreeableMemory (Option A) are both default CloudWatch metrics for Amazon RDS. CPUUtilization measures the percentage of CPU capacity used by the database instance. FreeableMemory reports the amount of available random access memory. Both are automatically published to CloudWatch every minute without additional setup. DatabaseConnections (Option E) is also a default metric, but in the context of this question, the two correct answers are CPUUtilization and FreeableMemory. QueryThroughput (Option C) is not a standard CloudWatch metric for RDS; it is available from Performance Insights. ReadThrottleEvents (Option D) is not a default metric; it is specific to DynamoDB or RDS with provisioned IOPS. Therefore, the correct answers are A and B.

Answer

QueryThroughput

Answer

ReadThrottleEvents

Answer

DatabaseConnections

Question 5

A database administrator runs the above CLI command. The DB instance has pending modifications. Which modification will take effect immediately without requiring a reboot?

Accepted Answer

BackupRetentionPeriod. The `--apply-immediately` flag causes eligible modifications to be applied immediately. Both `BackupRetentionPeriod` and `MasterUserPassword` are parameters that can be changed dynamically without requiring a reboot. `BackupRetentionPeriod` adjusts the backup schedule in the background, and `MasterUserPassword` updates the password instantly via the RDS API. In contrast, `DBInstanceClass` and `AllocatedStorage` require a reboot even with `--apply-immediately`.

Answer

DBInstanceClass

Answer

AllocatedStorage

Question 6

A database specialist sees the above output for an RDS MySQL instance. The application reports that the instance is not accepting writes. What is the most likely cause?

Accepted Answer

The instance is a read replica and cannot accept write requests.. The most likely cause is that the RDS MySQL instance is configured as a read replica. Read replicas in Amazon RDS are designed to handle read traffic only and do not accept write operations. Any attempt to write to a read replica will be rejected by the database engine, which matches the symptom described.

Answer

The allocated IOPS are insufficient for the write workload.

Answer

Multi-AZ is not enabled, so the instance cannot accept writes.

Answer

Storage encryption is enabled, which prevents write operations.

Question 7

A company is using a Multi-AZ RDS for MySQL instance. The primary instance recently experienced an unexpected failover, and the application experienced a brief interruption. The database administrator wants to investigate the root cause. Which AWS service should be used to review the failover event and its details?

Accepted Answer

Amazon RDS Event Notifications. Amazon RDS Event Notifications publish events related to DB instances, including failovers. They provide details such as the event source, message, and time, enabling root cause analysis. While AWS CloudTrail can record API calls that trigger failovers (e.g., RebootDBInstance with Failover), automatic failovers due to underlying issues are not captured as API calls. AWS Config tracks configuration changes, and AWS Trusted Advisor offers best practice checks but does not log specific events. Therefore, to review the failover event and its details, RDS Event Notifications is the most appropriate service.

Answer

AWS Config

Answer

AWS Support (Trusted Advisor)

Answer

AWS CloudTrail

Question 8

A company is running Amazon RDS for Oracle with a Multi-AZ deployment. The database is experiencing performance degradation due to high I/O waits. The team suspects that the issue is related to the transaction log (redo log) writes. Which THREE metrics should be monitored in Amazon CloudWatch to diagnose the issue?

Accepted Answer

DiskQueueDepth. Options A, C, and E are correct because high redo log sync time, high redo log file sync waits, and high disk queue depth are indicators of I/O bottlenecks affecting redo log writes. Option B is wrong because CPU utilization does not directly indicate redo log issues. Option D is wrong because read latency is not directly related to redo log writes.

Answer

CPUUtilization

Answer

ReadLatency

Question 9

A company is designing a disaster recovery plan for an Amazon RDS for Oracle DB instance. The primary region is us-east-1, and the DR region is us-west-2. The RPO must be less than 5 minutes, and the RTO must be less than 15 minutes. Which THREE actions should be taken? (Choose THREE.)

Accepted Answer

Create a cross-region read replica in us-west-2.. Amazon RDS for Oracle supports cross-region read replicas, which use asynchronous replication to keep the replica in us-west-2 within seconds of the primary. This can achieve an RPO of less than 5 minutes and, with manual promotion, an RTO of less than 15 minutes. Option B is correct because enabling cross-region automated backups copies backups to us-west-2, providing a baseline backup with a longer retention period. While automated backups alone cannot achieve a 5-minute RPO, they are a critical part of a comprehensive DR strategy, offering protection against data corruption and enabling point-in-time recovery. Option D is correct because AWS DMS with ongoing replication (change data capture) can replicate transactions from the source Oracle DB to a target in us-west-2 with sub-second latency, achieving the required RPO and RTO when combined with a pre-provisioned target.

Answer

Deploy a Multi-AZ standby in us-east-1.

Answer

Take daily manual snapshots and copy them to us-west-2.

Question 10

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 is incorrect because eventually consistent reads do not cause data loss; they may return stale data but not overwrite. Option B (LWW with unsynchronized clocks) is the correct cause. Option C is incorrect because TTL expiration would affect data in both regions, not cause loss after partition. Option D is incorrect because replication resumes after partition recovery, and replication does not stop permanently.

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 11

A database administrator sees repeated 'Aborted connection' warnings in the RDS for MySQL error log. The application team reports intermittent connection errors. What is the most likely cause of these aborted connections?

Accepted Answer

The application is closing the database connection abruptly without completing the handshake.. The 'Aborted connection' warning in RDS for MySQL typically occurs when a client fails to complete the initial handshake or disconnects abruptly before the authentication completes. This is often caused by the application closing the connection prematurely or a network interruption during the connection setup. Option A is incorrect because wait_timeout affects idle connections, not aborted connections during handshake. Option B is incorrect because a permission error would result in 'Access denied' rather than 'Aborted connection'. Option C is incorrect because memory pressure would cause performance degradation, not specifically these warnings.

Answer

The wait_timeout parameter is too low, causing idle connections to be terminated.

Answer

The user 'appuser' does not have permission to connect from host '10.0.0.50'.

Answer

The database instance is running out of memory, causing connection drops.

Question 12

A database specialist is configuring an Amazon RDS for PostgreSQL instance with automated backups enabled. The backup retention period is set to 7 days. The instance experiences a failure and becomes unavailable. What is the maximum amount of time the specialist has to recover the database to the most recent possible point in time?

Accepted Answer

7 days. With automated backups enabled and a retention period of 7 days, Amazon RDS for PostgreSQL allows point-in-time recovery to any point within the backup retention period, up to the latest restorable time (typically within the last 5 minutes). Therefore, the maximum time window for recovering to the most recent possible point in time is 7 days. Option A is incorrect because 1 hour is too short; the retention period covers up to 7 days. Option C is incorrect because 14 days exceeds the configured retention period of 7 days. Option D is incorrect because 35 minutes is not a standard limitation for point-in-time recovery; the restriction is the retention period.

Answer

1 hour

Answer

14 days

Answer

35 minutes

Question 13

A company is running an Amazon RDS for MySQL Multi-AZ DB instance. The primary instance in us-east-1a experiences an unexpected failure. After the automatic failover, the application team reports that write latency has increased significantly. The new primary instance is in us-east-1b. The DB instance class and storage configuration are identical. What is the MOST likely cause of the increased write latency?

Accepted Answer

The application is connecting to the DB instance in a different Availability Zone, increasing network latency.. After failover, the new primary DB instance resides in us-east-1b, while the application likely continues to connect to the original endpoint or is still running in us-east-1a. This cross-AZ network hop introduces additional latency for write operations, as the application must send data over the network between Availability Zones. The DB instance class and storage are identical, so performance differences are not due to hardware changes.

Answer

The DB instance class in us-east-1b is a different size than the original.

Answer

The Multi-AZ configuration uses asynchronous replication, causing higher latency.

Answer

The new primary is in the same Availability Zone as the application, but the standby is in a different AZ, causing synchronous replication overhead.

Question 14

A database administrator is troubleshooting an Amazon RDS for PostgreSQL DB instance that is experiencing high CPU utilization. The administrator runs the following query to find the current running queries:

SELECT pid, now() - pg_stat_activity.query_start AS duration, query, state
FROM pg_stat_activity
WHERE state = 'active';

The output shows a high number of queries with a state of 'active' and durations exceeding several minutes. What should the administrator do FIRST to reduce CPU utilization?

Accepted Answer

Use pg_terminate_backend to terminate the long-running queries.. The immediate cause of high CPU utilization is the long-running active queries consuming resources. Using pg_terminate_backend to terminate these queries will quickly free up CPU cycles, providing immediate relief. This is the first troubleshooting step before making configuration changes or scaling, as it directly addresses the symptom shown in the pg_stat_activity output.

Answer

Modify the max_connections parameter to limit concurrent sessions.

Answer

Scale up the DB instance to a larger instance class.

Answer

Enable pg_stat_statements to collect query performance data.

Question 15

A company is using Amazon DynamoDB with on-demand capacity mode. The application experiences occasional throttling during peak hours. The operations team wants to reduce throttling without changing the application code. What should they do?

Accepted Answer

Switch to provisioned capacity mode and configure auto scaling.. DynamoDB on-demand capacity mode does not allow manual adjustment of capacity units; it scales automatically but can still throttle if traffic exceeds the previous peak by a large margin. Switching to provisioned capacity mode with auto scaling allows you to set a higher minimum capacity and scale proactively based on actual usage patterns, reducing throttling without code changes. This approach gives more control over capacity limits while still automating adjustments.

Answer

Increase the read and write capacity units in the on-demand mode.

Answer

Enable DynamoDB Accelerator (DAX) to cache reads.

Answer

Use DynamoDB global tables to distribute traffic across regions.