DBS-C01 Practice Exam 61 — 20 Questions

Question 1

A database specialist manages an Amazon Aurora MySQL cluster that serves an internal reporting application. The security team wants a monthly record of who connected to the database, from which client host, and when the connection succeeded or failed, without modifying the application or enabling extended logging that increases storage costs. The cluster already publishes logs to Amazon CloudWatch Logs. Which action should the specialist take to capture this information with the LEAST operational effort?

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

Accepted Answer

Enable the audit log on the Aurora MySQL cluster by setting server_audit_logging to 1 and selecting the CONNECT event in server_audit_events.. Aurora MySQL includes the server audit plugin, which can log CONNECT events capturing the user, client host, and whether the attempt succeeded. Because the cluster already exports logs to CloudWatch Logs, enabling server_audit_logging and adding CONNECT to server_audit_events delivers the required monthly record with minimal effort and low storage impact.

Answer

Publish the Aurora MySQL error log to Amazon CloudWatch Logs and create a metric filter for failed logins.

Answer

Enable Performance Insights on the Aurora cluster and query the performance_schema tables for connection history.

Answer

Enable the general log on the Aurora MySQL cluster parameter group and set the log output to FILE.

Question 2

A company is migrating an on-premises MySQL database to Amazon Aurora MySQL. The database is 1 TB and the company wants to use AWS DMS for the migration. They need to ensure that the target Aurora cluster is highly available and can survive an Availability Zone failure. Which configuration should be used for the Aurora cluster?

Accepted Answer

Create an Aurora MySQL cluster with a writer instance and at least one reader instance in a different Availability Zone.. To ensure high availability and survive an Availability Zone failure, an Aurora MySQL cluster should have at least one reader instance in a different Availability Zone from the writer. Aurora automatically fails over to a reader if the writer becomes unavailable, providing minimal downtime. The storage layer is already replicated across three AZs, but the compute endpoint requires a reader for failover. Other options do not provide the necessary fault tolerance.

Answer

Create an Aurora MySQL cluster with a single writer instance and no reader instances.

Answer

Create an Aurora MySQL cluster with a writer instance and enable Aurora Backtrack.

Answer

Create an Aurora MySQL cluster with a writer instance and enable Multi-AZ deployment.

Question 3

A retailer is deploying an Amazon RDS for SQL Server Multi-AZ instance in a private subnet group. The database must be reachable only from application servers in the same VPC, and DBAs on the corporate network must connect through a bastion host. Which combination of settings should be used?

Accepted Answer

Set Publicly accessible to No, attach a security group that allows the database port from the application server security group and from the bastion host security group.. A non-publicly accessible instance in a private subnet group has only private addressing, satisfying the isolation requirement. Security groups that reference the application and bastion security groups as sources restrict access to exactly those instances on the database port, without hard-coding subnet ranges that could drift as the environment changes. This is the least-privilege connectivity pattern for the described topology.

Answer

Set Publicly accessible to Yes, attach a security group allowing the application subnet CIDR, and add an inbound rule for the bastion host's private IP address.

Answer

Set Publicly accessible to No and attach a network ACL that denies all inbound traffic except from the corporate network's public IP range.

Answer

Set Publicly accessible to Yes and place the instance in a public subnet, then rely on the DB subnet group to restrict which hosts can resolve the endpoint.

Question 4

A company runs an Amazon DynamoDB table that stores session data with a TTL attribute configured. A database specialist notices that expired items are still returned by GetItem and Query operations hours after their expiration timestamps. The table has provisioned capacity with plenty of unused write capacity. What is the MOST likely explanation and the appropriate action?

Accepted Answer

DynamoDB TTL deletion is asynchronous and can lag up to 48 hours, so items may still appear in reads. The specialist should filter expired items in application queries.. DynamoDB TTL deletion is intentionally asynchronous and may take up to roughly 48 hours after the expiration timestamp. Until the background process removes an item, reads can still return it, so applications should filter on the expiration attribute when immediate exclusion matters rather than expecting instant deletion.

Answer

The TTL attribute is stored as a string instead of a number in epoch seconds, so DynamoDB cannot process it. The specialist must rewrite the values as numbers.

Answer

The table's write capacity is being consumed by other workloads, so TTL deletions are throttled. The specialist should switch the table to on-demand capacity mode.

Answer

The TTL feature must be enabled separately on each global secondary index, otherwise expired items remain readable through index queries.

Question 5

A company uses Amazon DynamoDB with a table that has a global secondary index (GSI). The application team reports that writes to the base table occasionally fail with ProvisionedThroughputExceededException, even though the base table's write capacity seems sufficient. The GSI uses provisioned capacity. What is the most likely cause and the correct remediation?

Accepted Answer

The GSI's write capacity is insufficient for the projected writes; increase the GSI's write capacity units.. Writes to a DynamoDB base table also consume write capacity on every GSI that includes the modified attributes. If the GSI has lower provisioned write capacity than the base table, the GSI throttles the write and the base table write fails with ProvisionedThroughputExceededException. Increasing the GSI's write capacity units is the correct remediation.

Answer

The GSI's partition key is poorly chosen, causing hot partitions; switch the GSI to on-demand capacity mode.

Answer

The base table and GSI are in different AWS Regions; enable global tables to synchronize capacity.

Answer

The base table's partition key is hot; enable DynamoDB Streams to distribute the load.

Question 6

A database specialist is monitoring an Amazon Aurora MySQL cluster. The specialist notices that the writer instance's CPU utilization is consistently high, and the application experiences increased latency. The specialist suspects that the issue is due to a high number of row lock waits. Which two actions should the specialist take to diagnose and mitigate the issue? (Choose two.)

Accepted Answer

Enable Performance Insights and analyze the db.lock_wait metric.. To diagnose row lock waits in Aurora MySQL, the specialist should enable Performance Insights to monitor the db.lock_wait metric, which quantifies the load from lock waits. Additionally, querying the performance_schema.data_lock_waits table provides detailed information about blocking and waiting transactions. These two actions together allow identification of the problematic locks and the transactions involved, enabling targeted mitigation such as query optimization or killing blocking sessions.

Answer

Increase the innodb_lock_wait_timeout parameter to reduce lock wait errors.

Answer

Query the information_schema.INNODB_LOCKS table to identify blocking transactions.

Answer

Check the MySQL error log for messages about lock wait timeouts.

Question 7

A company runs an Amazon DynamoDB table with provisioned capacity and a global secondary index (GSI). The table experiences sudden spikes in write traffic, causing throttling on the GSI. The database specialist needs to reduce throttling on the GSI. (Choose two.)

Accepted Answer

Modify the GSI to use a different partition key with higher cardinality.. Throttling on a GSI can occur due to insufficient provisioned WCU or due to hot partitions from a poorly chosen partition key. Increasing the GSI's WCU provides more write capacity, while changing the partition key to a higher-cardinality attribute distributes the load more evenly. Both actions can reduce throttling. Other options like increasing base table WCU or enabling Streams do not directly address GSI capacity issues.

Answer

Increase the write capacity units (WCU) of the base table.

Answer

Switch the table to on-demand capacity mode.

Answer

Enable DynamoDB Streams on the table to capture write activity.

Question 8

A company is migrating an on-premises MySQL 8.0 database to Amazon Aurora MySQL. The database is 8 TB, and the business requires less than 15 minutes of downtime during cutover. The network link between the data center and AWS has 500 Mbps of available bandwidth. Which TWO steps should the team take to meet the downtime requirement? (Choose two.)

Accepted Answer

Enable binary logging on the source MySQL database and configure the AWS DMS source endpoint with the correct log position.. Meeting a 15-minute cutover for an 8 TB on-premises MySQL database requires continuous replication so the target stays current. AWS DMS full-load plus CDC copies the data once and then applies ongoing changes, and CDC requires binary logging on the source plus a valid log position in the DMS source endpoint. Together these allow a short final switchover rather than a bulk copy during the maintenance window.

Answer

Use AWS Snowball Edge to ship the 8 TB of data to Amazon S3 and then load it into Aurora MySQL with LOAD DATA FROM S3.

Answer

Create an Aurora MySQL read replica in the same AWS Region and promote it during the maintenance window.

Answer

Export the database with mysqldump and restore it into Aurora MySQL during the maintenance window.

Question 9

A company runs a production Amazon Aurora MySQL cluster. The database specialist must ensure that automated backups are retained for 35 days. The current backup retention period is 7 days. The specialist modifies the DB cluster's backup retention period to 35 days using the AWS CLI. What is the immediate effect of this change on existing automated backups?

Accepted Answer

Existing automated backups will be retained for 35 days from their original creation date, and new backups will also be retained for 35 days.. Increasing the automated backup retention period on an Amazon Aurora cluster immediately applies the new retention window to existing automated backups. Backups older than the new retention period are deleted, while those within the window are retained until they age out. This behavior ensures that the cluster's backup policy is consistently enforced without requiring manual backup management or a reboot.

Answer

Only new automated backups created after the change will be retained for 35 days; existing backups remain at 7 days retention.

Answer

The change requires a reboot of the DB cluster to take effect, and until then, backups continue to be retained for 7 days.

Answer

All existing automated backups are immediately deleted and new backups will be retained for 35 days.

Question 10

A database specialist is managing an Amazon DynamoDB table with a global secondary index (GSI). The table has a provisioned capacity mode with auto scaling enabled. The specialist notices that write operations to the base table are being throttled, even though the base table's write capacity is sufficient. What is the most likely cause?

Accepted Answer

The GSI's write capacity is insufficient, causing throttling on the base table.. DynamoDB writes to a base table are replicated to all associated GSIs. If any GSI lacks sufficient write capacity, the base table write can be throttled because the write must succeed on all indexes. The specialist should check the GSI's write capacity and consider enabling auto scaling or increasing provisioned capacity for the GSI to resolve the throttling.

Answer

Auto scaling is not enabled on the GSI, so it cannot scale to handle the write load.

Answer

The GSI's partition key is causing a hot partition, leading to throttling on the base table.

Answer

The base table's write capacity is insufficient, causing throttling on the GSI.

Question 11

A database specialist manages an Amazon Aurora MySQL cluster that serves an internal reporting application. The security team wants a monthly record of who connected to the database, from which client host, and when the connection succeeded or failed, without modifying the application or enabling extended logging that increases storage costs. The cluster already publishes logs to Amazon CloudWatch Logs. Which action should the specialist take to capture this information with the LEAST operational effort?

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

Accepted Answer

The reader instances are undersized for the analytical workload, causing them to fall behind the writer.. AuroraReplicaLag measures the delay between when a write is committed on the writer and when it is visible on a reader. High lag typically indicates that reader instances cannot apply changes quickly enough, often due to resource constraints. Analytical queries are resource-intensive and can compete with replication apply. Scaling up the reader instances provides more CPU and memory to handle both the queries and replication, reducing lag.

Answer

The reader instances are in a different Availability Zone than the writer, causing network latency that increases replication lag.

Answer

The Aurora cluster's backtrack feature is enabled, which is consuming resources on the reader instances.

Answer

The writer instance is experiencing high CPU utilization, causing it to delay sending binlogs to the readers.

Question 12

A database specialist manages an Amazon Aurora MySQL cluster that serves an internal reporting application. The security team wants a monthly record of who connected to the database, from which client host, and when the connection succeeded or failed, without modifying the application or enabling extended logging that increases storage costs. The cluster already publishes logs to Amazon CloudWatch Logs. Which action should the specialist take to capture this information with the LEAST operational effort?

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

Accepted Answer

Use Performance Insights to examine the Top SQL list, sorted by DB load, for the 7-day retention window.. Performance Insights stores up to 7 days of performance data at no additional cost and its Top SQL view orders statements by DB load, which represents cumulative active session time. That makes it the native, lowest-overhead way to find the statements consuming the most total time. Slow query logs, process list polling, and audit logs lack the aggregation or historical depth required.

Answer

Enable Aurora Advanced Auditing and analyze the audit logs with Amazon Athena to rank statements by total execution time.

Answer

Enable the slow query log on the cluster, then use Amazon CloudWatch Logs Insights to query the log group for the slowest statements over the past week.

Answer

Query the information_schema.PROCESSLIST table repeatedly with an AWS Lambda function and aggregate the results in Amazon S3.

Question 13

A company uses Amazon ElastiCache for Redis to cache session data for a web application. The cluster is configured with cluster mode disabled and has one primary node and two replica nodes. The database specialist needs to ensure that the cache remains available if the primary node fails. The specialist also wants to minimize data loss. Which configuration should the specialist use?

Accepted Answer

Enable Multi-AZ with automatic failover.. Multi-AZ with automatic failover automatically promotes a replica to primary if the primary fails, ensuring high availability. It also minimizes data loss by replicating data asynchronously to replicas in different Availability Zones. This is the standard configuration for ElastiCache for Redis when high availability is required with cluster mode disabled.

Answer

Enable AOF persistence with every write.

Answer

Configure a read replica in a different Availability Zone and manually promote it on failure.

Answer

Enable cluster mode and distribute data across shards.

Question 14

A company uses Amazon DynamoDB for an order-processing application. The operations team wants to be notified whenever write capacity consumption on a specific table exceeds a defined threshold for five consecutive minutes. The team has already enabled DynamoDB metrics in Amazon CloudWatch. What is the MOST operationally efficient way to implement this alerting?

Accepted Answer

Create a CloudWatch alarm on the ConsumedWriteCapacityUnits metric for the table with a period of 300 seconds and a threshold, and configure an Amazon SNS topic as the alarm action.. CloudWatch natively ingests DynamoDB's ConsumedWriteCapacityUnits metric, and an alarm with a 300-second period evaluates whether the threshold is breached for five continuous minutes. Wiring an SNS topic as the alarm action delivers the notification. Streams, CloudTrail data events, and Trusted Advisor all lack a per-table consumed-capacity metric with sustained-window evaluation.

Answer

Use AWS Trusted Advisor to monitor DynamoDB capacity and set up a notification when the check reports a warning.

Answer

Enable DynamoDB Streams on the table and use an AWS Lambda function to count write events, publishing to Amazon SNS when the count exceeds the threshold.

Answer

Configure AWS CloudTrail data events on the table and create an Amazon EventBridge rule that matches high-volume write API calls.

Question 15

A database specialist manages an Amazon Aurora MySQL cluster that serves an internal reporting application. The security team wants a monthly record of who connected to the database, from which client host, and when the connection succeeded or failed, without modifying the application or enabling extended logging that increases storage costs. The cluster already publishes logs to Amazon CloudWatch Logs. Which action should the specialist take to capture this information with the LEAST operational effort?

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

Accepted Answer

Reduce the number of concurrent INSERT sessions by batching or serializing writes to the table.. The LWLock:BufferContent wait event points to contention on shared buffer pages among concurrent writers. When many INSERT sessions target the same table, they compete for the same pages, causing lightweight lock waits and elevated commit latency. Reducing write concurrency through batching or serializing inserts minimizes page-level contention. Increasing max_connections or shared_buffers does not resolve the hot-page contention and may introduce downtime or worsen the issue.

Answer

Increase the value of the `max_connections` parameter in the DB cluster parameter group.

Answer

Modify the table to use unlogged mode so that INSERT operations bypass shared buffers.

Answer

Increase the `shared_buffers` parameter to allocate more memory for caching table pages.

Question 16

A company runs an Amazon RDS for MySQL Multi-AZ DB instance. During a maintenance window, the DB instance fails over to the standby. After failover, the application's connections through the original DNS endpoint fail for about a minute, then recover automatically. A database specialist must explain why the application recovered without any endpoint change. What is the reason?

Accepted Answer

The CNAME record of the DB instance endpoint is updated to point to the new primary, and clients that honor the record's short TTL reconnect to the new primary.. In a Multi-AZ DB instance deployment, failover promotes the standby and updates the DB instance endpoint's DNS CNAME to the new primary. Applications that reconnect by resolving the endpoint name recover automatically once the record's TTL expires and DNS propagates. This is why no endpoint configuration change is required on the client side, and why a brief connection interruption is expected.

Answer

The application uses the cluster endpoint, which automatically redirects connections to whichever node is currently the writer.

Answer

RDS Proxy maintains persistent client connections and transparently reconnects them to the new primary after failover.

Answer

The standby assumes the original primary's private IP address during failover, so existing connections continue to work without re-resolution.

Question 17

A database specialist manages an Amazon Aurora MySQL cluster that serves an internal reporting application. The security team wants a monthly record of who connected to the database, from which client host, and when the connection succeeded or failed, without modifying the application or enabling extended logging that increases storage costs. The cluster already publishes logs to Amazon CloudWatch Logs. Which action should the specialist take to capture this information with the LEAST operational effort?

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

Accepted Answer

Configure the application's connection pool to properly close connections after use and set a maximum pool size.. The application is opening connections without closing them, leading to connection exhaustion. The proper fix is to correct the connection pool configuration to close connections after use and set a maximum pool size. This prevents the leak and ensures connections are available. Monitoring or scaling the instance does not solve the root cause, and increasing max_connections only delays the problem.

Answer

Increase the max_connections parameter in the custom DB cluster parameter group and reboot the writer instance.

Answer

Enable Performance Insights and analyze the database load to identify the queries causing the timeouts.

Answer

Modify the Aurora cluster to use a larger instance class for the writer instance.

Question 18

A company runs an Amazon RDS for SQL Server DB instance in a single Availability Zone. The business requires the database to survive an Availability Zone failure with automatic failover and minimal downtime. Which change should the database specialist make to the DB instance?

Accepted Answer

Convert the DB instance to a Multi-AZ deployment so a standby is maintained in a different Availability Zone with automatic failover.. Converting the instance to a Multi-AZ deployment gives RDS SQL Server a synchronous standby in a second Availability Zone and automatic failover of the database endpoint, meeting the automatic and minimal-downtime requirements. Read replicas need manual promotion, backups require a lengthy restore, and Auto Scaling groups do not apply to RDS instances.

Answer

Enable automated backups with a 35-day retention period so the instance can be restored to another Availability Zone after a failure.

Answer

Create a read replica in another Availability Zone and manually promote it during an outage.

Answer

Place the DB instance in an Amazon EC2 Auto Scaling group across multiple Availability Zones.

Question 19

A database specialist manages an Amazon Aurora MySQL cluster that serves an internal reporting application. The security team wants a monthly record of who connected to the database, from which client host, and when the connection succeeded or failed, without modifying the application or enabling extended logging that increases storage costs. The cluster already publishes logs to Amazon CloudWatch Logs. Which action should the specialist take to capture this information with the LEAST operational effort?

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

Accepted Answer

Request a service quota increase for the table's on-demand write throughput limit.. In on-demand mode, DynamoDB automatically scales but is constrained by a default per-table throughput quota. Sudden spikes exceeding this quota cause throttling. Requesting a quota increase raises the limit, allowing the table to handle higher throughput without errors, which is the correct immediate action.

Answer

Enable DynamoDB Accelerator (DAX) for the table to offload write traffic.

Answer

Modify the table to use provisioned capacity mode with auto scaling enabled.

Answer

Increase the table's provisioned write capacity units (WCUs) to accommodate the peak traffic.

Question 20

A database specialist is troubleshooting an Amazon DynamoDB table that intermittently returns ThrottlingException to an application. The table uses on-demand capacity mode, and the application performs reads and writes with a mix of item sizes. The specialist wants to determine whether specific partitions are hot and whether request patterns exceed per-partition limits. (Choose two.)

Accepted Answer

Enable DynamoDB Contributor Insights for the table and review the most accessed partition keys in the report.. Contributor Insights reports the most accessed and most throttled partition keys, identifying hot keys directly. The ThrottledRequests and ReadThrottleEvents/WriteThrottleEvents metrics confirm throttling and show when it occurs. Used together, they distinguish partition-level hot spots from overall capacity pressure, which aggregate capacity metrics, streams, and auto-scaling logs cannot do for an on-demand table.

Answer

Inspect the ConsumedReadCapacityUnits and ConsumedWriteCapacityUnits metrics for the table in Amazon CloudWatch to see aggregate usage.

Answer

Turn on DynamoDB Streams with NEW_AND_OLD_IMAGES to capture the partition keys involved in throttled requests.

Answer

Use CloudWatch Logs Insights to query the table's auto-scaling logs for partition-level throttling events.