DBS-C01 Practice Exam 53 — 20 Questions

Question 1

A company runs a critical application on Amazon RDS for PostgreSQL with Multi-AZ deployment. The database is a db.r5.xlarge instance with 500 GB of Provisioned IOPS (io1) storage. The application writes a large volume of time-series data every 5 minutes. Recently, the team noticed that the replica lag between the primary and standby instance has increased to over 10 seconds during peak write periods. The application requires that the standby be within 5 seconds of the primary for disaster recovery purposes. The team has already verified that network latency between AZs is minimal, and the standby instance is the same size as the primary. The CloudWatch metric 'TransactionLogsDiskUsage' shows that the primary is generating logs at a high rate. Which combination of actions should the database administrator take to reduce the replica lag? (Choose the best option.)

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Increase the Provisioned IOPS on both the primary and standby instances to improve log write throughput. Increasing Provisioned IOPS on both the primary and standby instances improves I/O throughput for writing transaction logs, which is the bottleneck causing replica lag. Higher IOPS reduces the time needed to generate logs on the primary and apply them on the standby. Option A is incorrect because disabling synchronous commit would reduce durability and may still not achieve the required lag reduction. Option B is incorrect since the standby instance size is already equal to the primary; the issue is I/O performance, not compute capacity. Option C is incorrect because reducing batch frequency impacts application responsiveness and does not address the I/O bottleneck.

Answer

Disable synchronous commit on the primary to reduce log generation

Answer

Change the standby instance to a larger instance type (e.g., db.r5.2xlarge) to improve apply throughput

Answer

Reduce the batch write frequency to every 10 minutes to lower the log generation rate

Question 2

A company runs a production Amazon RDS for PostgreSQL Multi-AZ DB instance (db.r5.large) with 500 GB of General Purpose SSD (gp2) storage. The application experiences intermittent latency spikes every 15 minutes. Monitoring shows that during these spikes, the ReadIOPS metric on the primary instance spikes to 5,000 IOPS (the baseline is 1,500 IOPS), and the BurstBalance drops from 100% to 20% then recovers. There is no increase in CPU or connections. The application uses connection pooling with pgBouncer on an EC2 instance. The team has verified that no long-running queries or index scans are causing the spikes. Which action is MOST likely to resolve the intermittent latency?

Accepted Answer

Migrate the storage to gp3 with a baseline of 3,000 IOPS and 125 MB/s throughput.. The latency spikes are caused by gp2 storage burst credit exhaustion. The 500 GB gp2 volume has a baseline of 1,500 IOPS, but the workload spikes to 5,000 IOPS every 15 minutes, rapidly consuming burst credits. Migrating to gp3 provides a baseline of 3,000 IOPS and 125 MB/s throughput without relying on burst credits, thus eliminating the credit exhaustion issue. Option A (read replica) does not resolve the primary instance's write IOPS spikes. Option B (larger instance) does not address storage IOPS limitations; CPU and connections are already normal. Option D (scale storage to 1,000 GB) would increase the gp2 baseline to 3,000 IOPS and provide more burst credits, but gp3 offers a simpler, more cost-effective solution with consistent performance and no credit-based throttling.

Answer

Create a read replica and redirect read traffic to it.

Answer

Increase the DB instance to db.r5.xlarge to improve CPU and network performance.

Answer

Scale the storage to 1,000 GB to increase baseline IOPS and burst credits.

Question 3

A financial services company runs a critical application on Amazon RDS for PostgreSQL. The database stores sensitive customer financial data. The security team has mandated that all access to the database must be through IAM database authentication to eliminate the need for passwords. The application currently uses a master user password stored in AWS Secrets Manager. The DBA needs to implement IAM authentication without downtime. The application is deployed on Amazon ECS and connects to the database using a connection string. The DBA has already created an IAM role for the ECS task with a policy that allows rds-db:connect. The DBA has also modified the DB instance to require SSL. However, after making these changes, the application cannot connect. The error message indicates 'IAM authentication is not enabled for this user'. What step did the DBA miss?

Accepted Answer

The DBA did not create a database user that is set to use IAM authentication.. IAM database authentication requires that a database user be created with the IAM authentication method. Specifically, the user must be created with the CREATEROLE privilege and granted the rds_iam role. Without this step, the authentication fails even if the IAM role is correctly configured. Option B is incorrect because the IAM policy was already attached. Option C is incorrect because IAM authentication does not require a password; it uses authentication tokens. Option D is incorrect because the security group and port are not related to IAM authentication.

Answer

The DBA did not attach the IAM policy to the ECS task role.

Answer

The DBA did not enable the 'password' authentication method.

Answer

The DBA did not update the security group to allow traffic on port 5432.

Question 4

An application is receiving the error shown in the exhibit. The application uses connection pooling. The RDS instance is a db.r5.large with max_connections set to 1000. What is the most likely cause?

Accepted Answer

The connection pool in the application is not releasing idle connections.. If the application's connection pool does not release idle connections, it can exhaust the maximum connections even though max_connections is set appropriately. Option A is incorrect because if the security group blocked connections, the application would receive a timeout or 'connection refused' error, not an error indicating max connections are reached. Option B is incorrect because max_connections is set to 1000, which is the default for a db.r5.large instance and is typically sufficient; the instance size supports that value. Option D is incorrect because a different VPC would cause network connectivity issues (e.g., timeout) rather than a 'too many connections' error, which indicates the connection is established but the limit is reached.

Answer

The security group is blocking incoming connections.

Answer

The max_connections parameter is set too low for the instance size.

Answer

The RDS instance is in a different VPC than the application.

Question 5

A team is setting up a DMS migration task. The IAM policy above is attached to the DMS replication instance's IAM role. The team is unable to modify the target RDS instance's maintenance window during the migration. Which additional permission is missing?

Accepted Answer

Add 'rds:ModifyDBInstance' permission for the target RDS instance.. Modifying the target RDS instance's maintenance window requires the `rds:ModifyDBInstance` permission. The DMS replication instance's IAM role must have this permission for the target RDS instance to allow the migration task to adjust the maintenance window, which is necessary to prevent conflicts during ongoing replication. Without this permission, the DMS task cannot alter the maintenance window, even if the IAM role has other RDS permissions.

Answer

Add 'rds:ModifyOptionGroup' permission for the target RDS instance.

Answer

Add 'dms:ModifyReplicationInstance' permission for the DMS replication instance.

Answer

Add 'ec2:DescribeVpcs' permission to the policy.

Question 6

A company uses Amazon DynamoDB with a global secondary index (GSI) on a table that contains sensitive data. The security team requires that the GSI be encrypted with a different AWS KMS key than the base table. Can this be achieved, and if so, how?

Accepted Answer

No, DynamoDB encrypts the entire table and all its indexes with the same KMS key.. DynamoDB encrypts all data at rest using a single KMS key per table. The base table and all of its GSIs are encrypted with the same key. It is not possible to use a different KMS key for a GSI. Option A is wrong because the GSI cannot have a separate key. Option B is wrong because KMS key policies do not allow per-index encryption. Option D is wrong because the table and its GSIs always use the same key.

Answer

Yes, by using a custom KMS key policy that differentiates between table and index.

Answer

Yes, by specifying a different KMS key ID when creating the GSI.

Answer

No, but you can use a different KMS key for the table and then the GSI will automatically use a different key.

Question 7

Which TWO actions are recommended when deploying an Amazon RDS for MySQL instance in a production environment to ensure high availability and durability? (Choose two.)

Accepted Answer

Enable automated backups with a retention period of at least 7 days. Automated backups with a retention period of at least 7 days enable point-in-time recovery (PITR) within that window, which is critical for restoring a database to a specific second in the event of a failure or data corruption. This ensures durability by allowing you to recover from logical errors or accidental deletions, not just hardware failures. Option E is correct because Multi-AZ deployment automatically provisions and maintains a synchronous standby replica in a different Availability Zone, providing automatic failover for high availability without manual intervention.

Answer

Enable Enhanced Monitoring

Answer

Enable Performance Insights

Answer

Enable deletion protection

Question 8

A company uses Amazon RDS for Oracle for an OLTP application. The database experiences high CPU utilization during peak hours. The application is read-heavy and can tolerate eventually consistent reads. Which solution reduces CPU load on the primary database with minimal application changes?

Accepted Answer

Create an RDS read replica and direct read traffic to it. Creating an RDS Read Replica offloads read traffic from the primary Oracle instance, directly reducing CPU utilization on the primary. Since the application is read-heavy and tolerates eventually consistent reads, the replica’s asynchronous replication lag is acceptable. This solution requires minimal application changes—only modifying the connection string to route SELECT queries to the replica endpoint.

Answer

Implement Amazon ElastiCache to cache frequent queries

Answer

Upgrade to a larger instance type

Answer

Use DynamoDB Accelerator (DAX) as a cache layer

Question 9

A company is designing a document database on Amazon DocumentDB for a content management system. Which TWO design practices improve query performance and reduce costs?

Accepted Answer

Use appropriate indexes to support common query patterns.. In Amazon DocumentDB, only Option E (Use appropriate indexes to support common query patterns) is correct. Sharding (Option A) is not supported by DocumentDB. Options B, C, and D are incorrect because they would degrade performance or increase costs. Note: The question asks for two, but only one option is correct.

Answer

Shard data based on access patterns to distribute load.

Answer

Design documents to avoid joins by frequently using $lookup.

Answer

Avoid denormalization to maintain strict normal forms.

Answer

Store all documents in a single collection without indexes to reduce overhead.

Question 10

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.. 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 11

A company uses Amazon DynamoDB for a real-time analytics application. The table is provisioned with 1000 RCU and 500 WCU. Recently, the application experienced throttling on reads during a marketing campaign. The 'ConsumedReadCapacityUnits' metric shows spikes up to 2000 RCU. The 'ReadThrottleEvents' metric is high. The table has a global secondary index (GSI) that is also throttled. The application uses eventually consistent reads. The team wants to minimize costs while preventing throttling. The campaign traffic is predictable and occurs for 2 hours each day. What should the team do?

Accepted Answer

Enable auto scaling with a scheduled scaling action to increase RCU during the campaign.. The traffic is predictable and occurs for 2 hours daily. Scheduled auto scaling can increase RCU during the campaign and reduce it afterward, minimizing cost while preventing throttling. Option A is incorrect because permanently increasing RCU to 2000 would waste capacity during the other 22 hours, increasing costs unnecessarily. Option B is incorrect because DynamoDB Accelerator (DAX) adds cost and primarily caches base table reads, not global secondary index reads; the GSI is also throttled, so DAX may not fully resolve the issue, and scheduled scaling is more cost-effective for predictable patterns. Option D is incorrect because on-demand capacity mode is more expensive for predictable, sustained high traffic; auto scaling with a schedule is cheaper for this use case.

Answer

Increase the provisioned RCU to 2000 permanently.

Answer

Implement DynamoDB Accelerator (DAX) to cache reads.

Answer

Switch the table to on-demand capacity mode.

Question 12

A database administrator is troubleshooting a sudden increase in read latency on an Amazon RDS for PostgreSQL instance. The instance has 200 GB of General Purpose SSD (gp2) storage with 600 provisioned IOPS. The administrator notices that the average queue depth is consistently above 4. Which action is the MOST effective way to reduce read latency?

Accepted Answer

Migrate to an io1 volume with 3000 provisioned IOPS.. Migrating to an io1 volume with 3000 provisioned IOPS directly increases the available IOPS, addressing the high queue depth and reducing read latency. Option A is incorrect because Multi-AZ does not allow read traffic to the standby; the standby is only used for failover. Option B is incorrect because increasing the instance size may not resolve the I/O bottleneck if the issue is insufficient IOPS. Option D is incorrect because increasing the allocated storage for gp2 increases baseline IOPS (3 IOPS per GB), but the option specifies not changing IOPS, so it would not help; even if it did, 500 GB would provide 1500 IOPS, which may still not be sufficient.

Answer

Enable Multi-AZ deployment to offload reads to the standby.

Answer

Change the instance type to a larger size with more vCPUs.

Answer

Increase the allocated storage to 500 GB without changing IOPS.

Question 13

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.. Aurora MySQL does not rely on binlogs for point-in-time recovery (PITR); it uses its own storage-based recovery. Disabling binary logging eliminates binlog generation entirely, saving storage and reducing I/O overhead. Option A is incorrect because manually deleting binlog files is not recommended by AWS and does not address the root cause. Option B is incorrect because exporting binlogs to Amazon S3 does not reduce the storage consumed within the cluster volume. Option D is incorrect because reducing the retention period only limits how long binlogs are kept, but binlogs still accumulate and consume storage until they expire.

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 14

A company has an Amazon RDS for SQL Server DB instance that stores financial data. The security team requires that all database activity be monitored in real-time for suspicious queries. Which AWS service should be used to meet this requirement?

Accepted Answer

Amazon GuardDuty with RDS Protection. Amazon GuardDuty with RDS Protection provides real-time monitoring of database activity on Amazon RDS instances, analyzing SQL queries and detecting suspicious behavior such as SQL injection or unusual access patterns. Option A (AWS CloudTrail) is incorrect because it records API calls made to the AWS environment, not the database queries themselves. Option B (AWS Security Hub) is incorrect as it aggregates security findings from multiple AWS services but does not perform real-time database activity monitoring. Option D (Amazon Inspector) is incorrect because it is a vulnerability assessment service that scans for software vulnerabilities and unintended network exposure, not for database query threats.

Answer

AWS CloudTrail

Answer

AWS Security Hub

Answer

Amazon Inspector

Question 15

A company is using Amazon RDS for MySQL and notices that database connections are being rejected intermittently. The application logs show 'Too many connections' errors. The DB instance has 1000 max_connections. Which action should the DBA take to troubleshoot and resolve this issue without impacting performance?

Accepted Answer

Enable Performance Insights and review the 'DB Connections' metric to identify spikes and troubleshoot application connection pooling. Enabling Performance Insights allows the DBA to monitor the 'DB Connections' metric in near real-time, identify exactly when connection spikes occur, and correlate those spikes with application behavior. This diagnostic approach pinpoints the root cause—such as a connection leak or insufficient connection pooling—without making changes that could degrade performance. Increasing max_connections or lowering wait_timeout without understanding the usage pattern can lead to resource exhaustion or premature connection termination.

Answer

Increase the max_connections parameter to 5000 in the DB parameter group

Answer

Create a read replica to offload read traffic

Answer

Set the 'wait_timeout' parameter to a lower value to close idle connections faster

Question 16

A company uses Amazon CloudWatch to monitor an RDS for Oracle instance. They want to receive an alert when the database connection count exceeds 90% of the maximum connections. Which CloudWatch metric should be used to create the alarm?

Accepted Answer

DatabaseConnections. (DatabaseConnections) is correct because this metric tracks the number of client connections to the database instance, which directly reflects the connection count. To alert when connections exceed 90% of maximum connections, you would monitor DatabaseConnections and compare it to the instance's MaxConnections parameter. Option A (ActiveTransactions) is incorrect because it measures the number of concurrent transactions, not connections. Option C (ReadIOPS) and Option D (NetworkThroughput) are unrelated metrics for disk I/O and network traffic, respectively.

Answer

ActiveTransactions

Answer

ReadIOPS

Answer

NetworkThroughput

Question 17

A company runs an application that requires a relational database with high availability across multiple Availability Zones. The database must automatically failover with minimal downtime. Which AWS service meets these requirements?

Accepted Answer

Amazon RDS for MySQL with Multi-AZ deployment.. Amazon RDS for MySQL with Multi-AZ deployment automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary instance fails, Amazon RDS automatically fails over to the standby, typically within 60–120 seconds, providing high availability with minimal downtime. This meets the requirement for a relational database with automatic failover across multiple Availability Zones.

Answer

Amazon DynamoDB with global tables.

Answer

Amazon Redshift with cross-Region snapshots.

Answer

Amazon RDS for MySQL with a single instance.

Question 18

Refer to the exhibit. An RDS for PostgreSQL instance shows frequent checkpoints every 10 seconds. What is the most likely cause?

Accepted Answer

The 'max_wal_size' parameter is set too low, causing frequent WAL switches.. Frequent checkpoints in PostgreSQL are often caused by small WAL size settings. The 'max_wal_size' parameter controls the maximum size of WAL files before a checkpoint is triggered. If set too low, the database will perform checkpoints more frequently to recycle WAL segments. Option A is incorrect because autovacuum bloat does not directly cause frequent checkpoints. Option B is incorrect because storage space issues may cause other symptoms, but not specifically checkpoint frequency. Option C is incorrect because concurrent connections may increase workload but do not directly cause frequent checkpoints; the checkpoint timing is driven by WAL generation rate and WAL size limits.

Answer

Autovacuum is not running, causing bloat.

Answer

The instance is running out of storage space.

Answer

There are too many concurrent connections.

Question 19

A company is using Amazon RDS for PostgreSQL with Multi-AZ deployment. The database administrator needs to perform a minor version upgrade with minimal downtime. Which TWO actions should the administrator take? (Choose TWO.)

Accepted Answer

Test the upgrade on a separate non-production environment first.. Options B and D are correct. Testing the upgrade on a separate non-production environment first (B) is a best practice to verify compatibility and avoid issues. Scheduling the upgrade during the maintenance window (D) allows Amazon RDS to perform the upgrade automatically with a failover, minimizing downtime. Option A is incorrect because disabling Multi-AZ would eliminate the failover benefit and cause downtime. Option C is incorrect because minor version upgrades do not require modifying the DB parameter group; AWS RDS handles parameter compatibility automatically. Option E is incorrect because taking a snapshot is a good practice for recovery but does not reduce downtime during the upgrade.

Answer

Disable Multi-AZ before the upgrade to reduce complexity.

Answer

Modify the DB parameter group to set the new version parameters.

Answer

Take a snapshot of the DB instance before the upgrade.

Question 20

A company is migrating a 1 TB Oracle database to Amazon Aurora PostgreSQL using AWS DMS. They need to ensure minimal downtime and data consistency. Which TWO actions should the company take?

Accepted Answer

Enable change data capture (CDC) on the source Oracle database. Enabling Change Data Capture (CDC) on the source Oracle database allows AWS DMS to capture ongoing changes after the full load, enabling a near-zero downtime migration by continuously replicating transactions to the target Aurora PostgreSQL. Option C is correct because enabling data validation on the DMS task ensures that the data migrated is consistent between the source and target, verifying that no data loss or corruption occurred during the migration process.

Answer

Increase the target Aurora storage to 2 TB to avoid storage issues

Answer

Disable foreign key constraints on the target during migration

Answer

Use AWS Schema Conversion Tool to convert the schema