DBS-C01 Practice Exam 58 — 20 Questions

Question 1

Refer to the exhibit. A database engineer runs the query above to troubleshoot an application error. The query returns no results even though the database is generating errors. What is the most likely reason?

Accepted Answer

The log stream format uses a different field name for the error message. Option D is correct because the query filters on the 'message' field, but the log stream format may have the error message in a different field. Option A is wrong because the query already uses case-insensitive matching. Option B is wrong because the log group configuration does not affect the query field names. Option C is wrong because the query does not specify a time range, but that would return results from the last 15 minutes by default.

Answer

The regex pattern does not match because it is case-sensitive

Answer

The query does not specify a time range, so no results are returned

Answer

The log group has not been configured to export to CloudWatch Logs

Question 2

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle using AWS DMS. The source database is 2 TB and has high transaction volume. The migration needs minimal downtime. Currently, full load completes but CDC task fails with 'ORA-1555: snapshot too old' errors. What should the DBA do to resolve this?

Accepted Answer

Increase the undo retention period and undo tablespace size on the source Oracle database.. Snapshot too old error occurs when undo data is overwritten. Increasing undo retention and tablespace size allows DMS to read consistent data. Option A is correct. Option B reduces performance. Option C increases log volume. Option D may cause data loss.

Answer

Restart the migration with a new full load and use a smaller task.

Answer

Enable supplemental logging on the source and use a larger DMS instance.

Answer

Reduce the transaction volume by pausing non-essential transactions during CDC.

Question 3

A financial services company runs an Amazon Aurora MySQL database cluster with a single writer and two readers. The cluster handles critical transactional workloads. Over the past month, the database experienced intermittent read replica lag spikes that caused stale reads in application queries. The database administrator needs to identify the root cause and reduce replica lag. Which THREE steps should the administrator take to diagnose and mitigate the issue?

Accepted Answer

Use Performance Insights on the reader instances to identify high-load queries causing resource contention.. Option A is correct because analyzing slow query logs helps identify long-running queries on the writer that may cause replication delay. Option B is correct because increased binary log retention can lead to lag; reducing it can help. Option C is correct because using Performance Insights on readers reveals resource bottlenecks. Option D is wrong because disabling Multi-AZ does not affect replica lag. Option E is wrong because upgrading readers to the same instance class as the writer may not address the root cause if the issue is on the writer side.

Answer

Switch from a single-writer cluster to Multi-AZ DB instance to reduce replication lag.

Answer

Upgrade the reader instances to a larger instance class to match the writer.

Question 4

A company is using Amazon DynamoDB for a gaming application. The application stores player scores in a table with a partition key of player_id and a sort key of timestamp. The company wants to query the top 10 scores for a given player efficiently. Which TWO steps should the company take to optimize this query?

Accepted Answer

Use the Query API with the LSI and scan index forward set to false to get the top scores.. A local secondary index (LSI) on score allows efficient sorting within a partition. A global secondary index (GSI) on score would not be efficient for per-player queries. The correct options are A and D. Option B (GSI) would not help per-player sorting. Option C (scan) is inefficient. Option E (LSI on timestamp) is already present.

Answer

Use a Scan operation with a filter expression to retrieve the top scores.

Answer

Create a local secondary index on the timestamp attribute.

Answer

Create a global secondary index (GSI) on the score attribute.

Question 5

A company is running an Amazon Redshift cluster with a single node. They need to improve query performance for large analytical workloads. Which action would provide the most immediate performance improvement?

Accepted Answer

Increase the number of nodes in the cluster.. Option C is correct because adding more nodes to the cluster distributes the workload and improves parallelism. Option A is wrong because using a single node, distributing data across slices is limited. Option B is wrong because compression is already used typically. Option D is wrong because VACUUM reclaims space but does not significantly improve performance for large workloads.

Answer

Distribute the data across all slices.

Answer

Apply compression encodings to all columns.

Answer

Run the VACUUM command to reclaim space.

Question 6

A company runs a production Amazon RDS for PostgreSQL instance with Multi-AZ deployment. The DB instance has a large number of connections from application servers. The operations team wants to monitor the number of database connections and receive an alert when it exceeds 80% of the maximum connections. Which combination of steps should be taken to set up this monitoring? (Choose two.)

Accepted Answer

Set the alarm threshold to (0.8 * max_connections) and the evaluation period to 1 minute. Correct answers are B and D. B: Create a CloudWatch alarm using the 'DatabaseConnections' metric. D: Set the alarm threshold to 80% of max_connections and the period to 1 minute for timely alerts. A is wrong because RDS Performance Insights does not provide connection count metrics via CloudWatch. C is wrong because Enhanced Monitoring provides OS metrics, not DB connection counts. E is wrong because the max_connections parameter should be checked from the DB parameter group, not the alarm.

Answer

Set the alarm threshold to 80 and the evaluation period to 5 minutes

Answer

Enable Enhanced Monitoring and create a CloudWatch alarm on the 'database_connections' metric

Answer

Enable Performance Insights and create a CloudWatch alarm using the 'DBLoad' metric

Question 7

A company is designing a disaster recovery strategy for an Amazon Aurora MySQL database with a recovery point objective (RPO) of 1 second and a recovery time objective (RTO) of 1 minute. Which TWO solutions meet these requirements? (Choose TWO.)

Accepted Answer

Deploy an Aurora Global Database with a secondary region.. Option A: Aurora Global Database provides replication across regions with RPO of seconds and RTO of minutes. Option D: Cross-Region read replicas can be promoted quickly. Option B: Multi-AZ is within region, not cross-region DR. Option C: Automated backups have RPO of 5 minutes. Option E: Snapshots are not frequent enough.

Answer

Use a Multi-AZ DB cluster deployment.

Answer

Take manual snapshots every hour and copy to another region.

Answer

Enable automated backups and perform point-in-time recovery in another region.

Question 8

A company is using Amazon DynamoDB with auto scaling enabled. The table's read capacity is set to a minimum of 100 and maximum of 1000 read capacity units (RCUs). The actual consumed read capacity is consistently at 200 RCUs. What should the database specialist do to optimize costs without impacting performance?

Accepted Answer

Lower the minimum read capacity to 200 RCUs.. Option A is correct because lowering the minimum to 200 RCUs ensures auto scaling does not scale below the actual usage, reducing provisioned capacity costs. Option B is wrong because decreasing the maximum could cause throttling during spikes. Option C is wrong because increasing the minimum would increase costs unnecessarily. Option D is wrong because disabling auto scaling would require manual management and may lead to over-provisioning.

Answer

Increase the minimum read capacity to 500 RCUs.

Answer

Disable auto scaling and set the read capacity to 200 RCUs.

Answer

Decrease the maximum read capacity to 500 RCUs.

Question 9

A database engineer is troubleshooting an Amazon Aurora MySQL DB cluster that is experiencing frequent failovers. The failovers are occurring during periods of low write activity. The engineer notices that the primary instance's writer endpoint is being used for read traffic from a legacy application. What is the most likely cause of the failovers?

Accepted Answer

The primary instance is overloaded due to read traffic from the writer endpoint. Option D is correct because using the writer endpoint for read traffic can overload the primary instance and cause failovers. Option A is wrong because the issue is not about replica lag. Option B is wrong because there is no mention of storage issues. Option C is wrong because failovers do not cause write blocking; they are the result.

Answer

A high replication lag between the primary and replica instances

Answer

A long-running write transaction is blocking the failover

Answer

Insufficient storage for the Aurora cluster volume

Question 10

Refer to the exhibit. A database engineer runs the command and receives the above output. The engineer wants to convert the database to Multi-AZ. Which command should be used?

Accepted Answer

aws rds modify-db-instance --db-instance-identifier mydb --multi-az. Option B is correct because 'modify-db-instance' with --multi-az is the correct AWS CLI command to enable Multi-AZ. Option A is wrong because 'create-db-instance' is for new instances, not modifying existing ones. Option C is wrong because 'reboot-db-instance' restarts the instance but does not change Multi-AZ. Option D is wrong because 'create-db-cluster' is for Aurora, not for converting a single DB instance to Multi-AZ.

Answer

aws rds reboot-db-instance --db-instance-identifier mydb --force-failover

Answer

aws rds create-db-instance --db-instance-identifier mydb --multi-az

Answer

aws rds create-db-cluster --db-instance-identifier mydb --multi-az

Question 11

A company runs an Amazon RDS for SQL Server database. The database size is 500 GB. The company needs to create a test environment with a copy of the production database that refreshes daily. Which THREE steps should be taken to automate this? (Choose THREE.)

Accepted Answer

Use AWS Backup or AWS Lambda to take a manual snapshot of the production DB instance daily.. Option A creates a snapshot, Option B restores to a new instance, Option D updates the application endpoint. Option C is unnecessary because restoring from snapshot does not require backup. Option E is not needed as snapshot already provides point-in-time.

Answer

Create a read replica of the production instance and promote it to the test environment.

Answer

Enable automated backups on the test instance after restoration.

Question 12

A company is using Amazon ElastiCache for Redis to cache database query results. The cache cluster is a single node. The application experiences increased latency when the cache misses. Which TWO actions can improve the cache hit ratio?

Accepted Answer

Increase the Time-to-Live (TTL) for cached items.. Options A and E are correct. Option A: Increasing the TTL keeps data in cache longer, reducing misses. Option E: Using lazy loading caches data on demand, which can improve hit ratio over time. Option B is wrong because decreasing TTL would increase misses. Option C is wrong because more read replicas do not improve hit ratio; they improve read throughput. Option D is wrong because disabling persistence does not affect hit ratio.

Answer

Disable persistence to free memory.

Answer

Decrease the Time-to-Live (TTL) for cached items.

Answer

Add read replicas to the ElastiCache cluster.

Question 13

A company uses Amazon DynamoDB for a gaming application. During a new game launch, the table experiences throttling on write requests. The table has a provisioned capacity of 10,000 WCU and 5,000 RCU. The write traffic pattern shows spikes up to 15,000 WCU for 5 minutes. Which action would resolve the throttling with minimal cost impact?

Accepted Answer

Enable Auto Scaling for DynamoDB with a target utilization of 70%. Option D is correct because DynamoDB Auto Scaling can handle the spikes by scaling up and down, reducing costs. Option A is wrong because doubling WCU would be costly and unnecessary. Option B is wrong because DynamoDB Accelerator (DAX) is for read performance, not writes. Option C is wrong because SQS would add latency and complexity.

Answer

Use Amazon SQS to buffer the write requests

Answer

Increase the provisioned WCU to 20,000 permanently

Answer

Enable DynamoDB Accelerator (DAX) for the table

Question 14

An e-commerce company uses Amazon ElastiCache for Redis as a session store for its web application. The application experiences occasional latency spikes during flash sales. The operations team notices that the Redis cluster's CPU utilization reaches 90% during these events. The current cluster is a single shard with a cache.r5.large node. The team wants to reduce CPU utilization and improve performance. What should the database administrator do?

Accepted Answer

Add read replicas to offload read traffic from the primary node.. Option B is correct because adding read replicas distributes read traffic, reducing CPU load on the primary. Option A is wrong because increasing retention does not reduce CPU. Option C is wrong because disabling persistence reduces durability but does not significantly reduce CPU. Option D is wrong because enabling encryption adds CPU overhead.

Answer

Increase the number of replicas for data durability.

Answer

Disable AOF persistence to reduce write overhead.

Answer

Enable encryption at rest to secure data.

Question 15

A database specialist observes the CloudWatch metric for a production RDS for MySQL instance. The max_connections parameter is set to 150. The Sum of DatabaseConnections over 1-minute periods is shown. The application reports intermittent connection failures. What is the most likely cause?

Accepted Answer

The number of connections exceeded the max_connections limit.. Option A is correct because the Sum metric over 1-minute period represents the total number of connections during that minute. A Sum of 200 indicates that at some point during the minute, connections exceeded the max_connections of 150, causing failures. Option B is wrong because the metric shows Sum, not average. Option C is wrong because connection pooling reduces connections, not increases. Option D is wrong because the metric clearly shows high connection counts.

Answer

The average number of connections is below the limit.

Answer

The DatabaseConnections metric is unreliable.

Answer

The application is not using connection pooling.

Question 16

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database is 500 GB in size and has a 24/7 uptime requirement. The migration window is limited to 2 hours. Which strategy should be used to minimize downtime?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication. Option C is correct because AWS DMS can replicate ongoing changes and allow a short cutover window. Option A is wrong because AWS SCT does not handle data migration. Option B is wrong because restoring a snapshot takes longer than 2 hours for 500 GB. Option D is wrong because Export/Import requires downtime and is slow.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and copy data

Answer

Take an on-premises backup and restore to RDS using Oracle RMAN

Answer

Export the database to a dump file and import into RDS

Question 17

A company uses Amazon RDS for PostgreSQL with a single-AZ deployment. The operations team needs to ensure that the database is available during a planned maintenance event that requires a reboot. The maintenance window is set for 30 minutes. The database size is 200 GB and the application can tolerate a few minutes of downtime. Which action should the team take to minimize downtime during the reboot?

Accepted Answer

Modify the DB instance to be Multi-AZ. Option C is correct because enabling Multi-AZ allows a failover to the standby with minimal downtime during maintenance. Option A is wrong because a manually created snapshot does not reduce downtime during a reboot. Option B is wrong because read replicas do not automatically take over on reboot. Option D is wrong because a DB instance restart still requires the instance to be unavailable during reboot.

Answer

Take a manual snapshot before the maintenance window and restore it if needed

Answer

Create a read replica and promote it to primary after the reboot

Answer

Schedule the reboot during a low-traffic period

Question 18

An IAM user has the policy shown. The user is trying to restore a DB instance from a manual snapshot using the AWS CLI. The restore fails with an access denied error. What is the most likely reason?

Accepted Answer

The policy does not grant the rds:RestoreDBInstanceFromDBSnapshot action on the DB instance resource.. Option D is correct because the restore action (RestoreDBInstanceFromDBSnapshot) requires permissions on both the snapshot and the DB instance resource. The policy allows the action on snapshot resources but not on the DB instance resource for the restore action itself. Option A is wrong because the snapshot resource ARN includes '*', which covers all snapshots. Option B is wrong because the action is allowed. Option C is wrong because the snapshot exists.

Answer

The rds:RestoreDBInstanceFromDBSnapshot action is misspelled.

Answer

The snapshot is encrypted and the user does not have permission to use the KMS key.

Answer

The snapshot resource ARN does not include the specific snapshot ID.

Question 19

A company is running an Amazon RDS for SQL Server instance and wants to automate the patching of the database engine. Which AWS service should be used?

Accepted Answer

AWS Systems Manager Patch Manager. Option C is correct because AWS Systems Manager Patch Manager can automate patching of RDS instances. Option A is wrong because RDS Automated Backups are for backups, not patching. Option B is wrong because RDS Maintenance Windows handle minor engine versions but not OS patching. Option D is wrong because AWS Config is for configuration compliance.

Answer

AWS Config

Answer

Amazon RDS Automated Backups

Answer

Amazon RDS Maintenance Window

Question 20

A company runs an Amazon Aurora MySQL database with read replicas to handle read traffic. During a recent load test, the primary instance CPU utilization reached 90%, but read replicas remained below 50%. The application uses a custom ORM that connects to a single endpoint. Which change will best distribute read traffic?

Accepted Answer

Configure the application to use the Aurora reader endpoint for read queries.. Aurora read replicas are accessed through the reader endpoint, not the cluster endpoint. Option A is correct. Option B is wrong because read replicas use reader endpoint. Option C is not a feature of Aurora. Option D is incorrect because ProxySQL is not needed.

Answer

Use Amazon RDS Proxy with read/write splitting.

Answer

Place the read replicas behind an Application Load Balancer.

Answer

Enable Aurora Auto Scaling for replicas and use the cluster endpoint for both read and write.

DBS-C01 Practice Exam 58 — 20 Questions

Exhibit

DBS-C01 Practice Exam 58 — 20 Questions

Exhibit