DBS-C01 Practice Exam 56 — 20 Questions

Question 1

A database specialist runs the CLI command shown. The output indicates the instance is Multi-AZ and available. The application, however, is experiencing intermittent connection timeouts to the database endpoint. What is the most likely cause?

Accepted Answer

A failover occurred due to a Multi-AZ event.. Option B is correct because Multi-AZ failover can cause transient connection timeouts if the application does not have proper retry logic. Option A is wrong because the instance status is 'available', not 'storage-full'. Option C is wrong because MySQL 8.0.28 is a supported version. Option D is wrong because the instance class is db.r5.xlarge, which is a current generation instance.

Answer

The MySQL engine version is not supported.

Answer

The DB instance class is not available in the current region.

Answer

The database storage is full.

Question 2

A database administrator is monitoring Amazon RDS for PostgreSQL using CloudWatch. The DB instance shows high CPU utilization, but the number of connections is normal. What is the most likely cause of the high CPU utilization?

Accepted Answer

There are long-running queries or missing indexes causing high CPU usage.. Option B is correct because high CPU utilization with normal connections often indicates inefficient queries or missing indexes causing full table scans. Option A is incorrect because burst balance is for gp2 storage, not CPU. Option C is incorrect because insufficient memory usually causes swapping, not high CPU. Option D is incorrect because ReadReplicas do not affect CPU on the primary instance.

Answer

The DB instance has a low burst balance for gp2 storage.

Answer

The instance is low on memory and is swapping.

Answer

The DB instance has a large number of Read Replicas.

Question 3

Refer to the exhibit. A database administrator runs the AWS CLI command to check the status of an Amazon RDS MySQL DB instance. Based on the output, what action is required to apply the pending modifications?

Accepted Answer

Reboot the DB instance to apply the pending parameter group changes.. Option C is correct because the ParameterApplyStatus is 'pending-reboot', indicating that a reboot is required to apply the parameter changes. The backup window change and password update are also pending, but the parameter group changes specifically require a reboot. Option A is incorrect because modifying the backup window does not require a reboot. Option B is incorrect because modifying the DB parameter group is already done; the status shows pending-reboot. Option D is incorrect because a snapshot is not required to apply changes.

Answer

Take a snapshot of the DB instance before applying changes.

Answer

Modify the DB parameter group to change the parameter values.

Answer

Modify the DB instance to set the backup retention period to 7.

Question 4

A company uses Amazon ElastiCache for Redis to cache frequently accessed data. The cache cluster experiences high CPU utilization during peak hours. The cluster has a single node of type cache.r5.large. What is the most cost-effective way to reduce CPU utilization while maintaining performance?

Accepted Answer

Add a read replica to distribute read traffic.. Option A is correct. Adding a read replica (sharing read traffic) reduces CPU on the primary. Option B is wrong because increasing to a larger node type is more expensive than adding replicas. Option C is wrong because increasing maxmemory-policy does not reduce CPU. Option D is wrong because enabling encryption adds overhead.

Answer

Enable encryption at rest and in transit.

Answer

Upgrade to a cache.r5.xlarge node type.

Answer

Increase the maxmemory-policy parameter to 'allkeys-lru'.

Question 5

A data warehouse team is migrating from Amazon Redshift to Amazon Redshift RA3 nodes. The current cluster uses 10 DC2.large nodes. The new cluster will use 4 RA3.xlarge nodes. After the migration, the team notices that query performance is significantly slower. Which factor is the MOST likely cause of the performance degradation?

Accepted Answer

The cluster has fewer nodes, reducing parallelism.. Option A is correct because RA3 nodes use managed storage and compute is separate; fewer nodes reduce parallel processing capability. Option B is incorrect because RA3 nodes are designed for large data. Option C is incorrect because RA3 nodes have managed storage; disk space is not the issue. Option D is incorrect because the number of slices per node is lower in RA3, but the primary factor is fewer nodes.

Answer

The data distribution style is set to EVEN instead of KEY.

Answer

The cluster does not have enough disk space for the workload.

Answer

RA3 nodes are not optimized for large datasets.

Question 6

A company's production RDS for PostgreSQL instance experienced a failover to the standby replica. After the failover, the application team reports that writes are failing with 'ReadOnlyException: Connection is read-only'. The DB instance status in the RDS console shows 'available'. Which action should the database administrator take to resolve the issue?

Accepted Answer

Update the application connection string to use the new writer endpoint from the RDS console.. Option B is correct because after a failover, the old primary becomes a standby and is read-only. The application must update its connection string to point to the new writer endpoint. Option A is wrong because rebooting forces another failover, not a resolution. Option C is wrong because modifying the DB instance does not change the endpoint. Option D is wrong because a read replica has a different use case.

Answer

Create a read replica and promote it to a new primary.

Answer

Reboot the DB instance to force a failover back to the original primary.

Answer

Modify the DB instance to enable Multi-AZ again.

Question 7

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database is 2 TB in size and has a tight migration window of 8 hours. Which THREE steps should be taken to minimize downtime during the migration?

Accepted Answer

Use AWS Database Migration Service (AWS DMS) with ongoing replication.. Option B is correct because AWS DMS can perform continuous replication. Option C is correct because using a large instance reduces migration time. Option E is correct because disabling backups during migration reduces overhead. Option A is wrong because AWS SCT is for schema conversion, not data migration. Option D is wrong because manual snapshot is for backup, not migration.

Answer

Take a manual snapshot of the source database before migration.

Answer

Use AWS Schema Conversion Tool (AWS SCT) to convert the schema.

Question 8

A company is deploying an Amazon Aurora MySQL database. The company requires that the database withstand the loss of two copies of data without impacting write availability. Which configuration should the company use?

Accepted Answer

Aurora with 6 copies of data across 3 Availability Zones. Aurora stores 6 copies of data across 3 AZs. The loss of two copies can be tolerated if they are distributed. Option A (3 copies in 3 AZs) is incorrect; Aurora uses 6 copies. Option B (2 copies in 2 AZs) is not correct. Option D (3 copies in 2 AZs) is not standard. The correct answer is C because Aurora's architecture provides higher durability.

Answer

Aurora with 3 copies of data in 3 Availability Zones

Answer

Aurora with 2 copies of data in 2 Availability Zones

Answer

Aurora with 3 copies of data in 2 Availability Zones

Question 9

A company is running a MongoDB-compatible Amazon DocumentDB cluster. The application experiences high write latency during peak hours. The database administrator checks the CloudWatch metrics and notices that the Write IOPS metric is consistently at the maximum for the instance size. What should the administrator do to reduce write latency?

Accepted Answer

Increase the instance size to a larger instance class with higher IOPS limits.. Option A is correct because increasing the instance size provides more IOPS capacity, which can reduce write latency if the instance is hitting IOPS limits. Option B is incorrect because enabling Multi-AZ adds a standby but does not increase write IOPS capacity on the primary. Option C is incorrect because increasing the storage size may increase IOPS if using gp2 but not necessarily, and the issue is IOPS, not storage capacity. Option D is incorrect because the instance class is already optimized for memory; the issue is I/O, not memory.

Answer

Switch to a memory-optimized instance class.

Answer

Increase the allocated storage size to improve I/O performance.

Answer

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

Question 10

Refer to the exhibit. A database administrator runs the AWS CLI command to retrieve CloudWatch metrics for an Amazon RDS DB instance. The output shows a spike in WriteLatency at 10:05 UTC. What is the most likely cause of this spike?

Accepted Answer

The DB instance's gp2 volume has exhausted its burst credits.. Option A is correct because a sudden spike in write latency often indicates that the storage volume has exhausted its burst credits and is now using baseline performance, which may be slower. Option B is incorrect because a large number of connections typically causes increased CPU and memory usage, not necessarily a latency spike. Option C is incorrect because a Multi-AZ failover would cause a brief downtime, not a latency spike. Option D is incorrect because a snapshot would cause I/O suspension, not a latency spike.

Answer

The DB instance is in the process of taking a snapshot.

Answer

There is a large number of concurrent connections to the DB instance.

Answer

The DB instance experienced a Multi-AZ failover.

Question 11

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The DBA receives an alert that the standby replica is lagging behind the primary. Which TWO actions should the DBA take to investigate the issue? (Choose TWO.)

Accepted Answer

Verify network latency between the primary and standby.. Option A and Option C are correct. Option A checks the replication lag metric. Option C checks network latency, which can affect replication. Option B is wrong because Multi-AZ does not have read replicas. Option D is wrong because storage type does not directly cause lag. Option E is wrong because Multi-AZ uses synchronous replication, not async.

Answer

Check the 'Replica Lag' metric for any read replicas.

Answer

Increase the allocated storage to improve IOPS.

Answer

Change the replication type from asynchronous to synchronous.

Question 12

A company runs a critical Amazon DynamoDB table with on-demand capacity. The table experiences throttling errors (ProvisionedThroughputExceededException) during peak hours. The table has a global secondary index (GSI) with a different partition key. What is the MOST likely cause of the throttling?

Accepted Answer

The global secondary index is throttling due to uneven access patterns.. Option C is correct because on-demand tables can throttle if a GSI's write capacity is exceeded. Option A is incorrect because on-demand capacity scales automatically for the base table. Option B is incorrect because throttling is not due to read-heavy workloads on the base table. Option D is incorrect because partition keys are automatically managed.

Answer

The base table's write capacity is insufficient for the workload.

Answer

The partition key design causes hot partitions in the base table.

Answer

The table's read capacity is too low for the read-heavy workload.

Question 13

A company is using Amazon DynamoDB with Auto Scaling enabled. During a flash sale, write traffic spikes and the application experiences ProvisionedThroughputExceededException errors. The DynamoDB table has provisioned write capacity of 1000 WCU and Auto Scaling is set to scale between 1000 and 10000 WCU. What is the most likely cause of the throttling?

Accepted Answer

Auto Scaling cannot react quickly enough to sudden traffic spikes.. Option D is correct because Auto Scaling reacts to actual consumption, but there is a lag; sudden spikes throttle before capacity increases. Option A is wrong because Auto Scaling does not have a maximum limit issue. Option B is wrong because throttling is due to write capacity, not partitioning. Option C is wrong because burst capacity is limited; sustained spikes require pre-warming or use of on-demand.

Answer

The DynamoDB table has insufficient partitions to handle the traffic.

Answer

The table's burst capacity is exhausted and Auto Scaling has not yet increased capacity.

Answer

The Auto Scaling policy has a maximum WCU limit that is too low.

Question 14

A company is running an Amazon RDS for MySQL DB instance. The database performance has degraded over time, and the company suspects that slow queries are the cause. Which AWS service should the company use to identify the slow queries and analyze the database performance?

Accepted Answer

Amazon RDS Performance Insights. Performance Insights provides a dashboard to analyze database performance and identify slow queries. CloudWatch Logs (A) is for logs, not query analysis. RDS Enhanced Monitoring (B) provides OS metrics, not query details. AWS Trusted Advisor (D) provides best-practice checks, not query analysis.

Answer

AWS Trusted Advisor

Answer

Amazon RDS Enhanced Monitoring

Answer

Amazon CloudWatch Logs

Question 15

A company is migrating a large on-premises Oracle database to Amazon RDS for Oracle. The database is 5 TB in size, and the migration must be completed within a week. The company has a dedicated 10 Gbps AWS Direct Connect connection. Which TWO AWS services should the company use to minimize downtime during the migration?

Accepted Answer

AWS Schema Conversion Tool (AWS SCT). AWS DMS can handle ongoing replication to minimize downtime. AWS SCT can convert the schema if needed, and AWS DMS can migrate data. AWS Snowball is for offline data transfer, which may not be needed with Direct Connect. AWS RDS is the target, not a migration service. AWS DataSync is for file data, not databases. The correct options are B and D.

Answer

AWS DataSync

Answer

AWS Snowball

Answer

Amazon RDS for Oracle

Question 16

A company uses Amazon DynamoDB with provisioned capacity. The application team reports occasional ProvisionedThroughputExceededException errors. The database administrator notices that the errors occur during periods of high traffic. What is the most cost-effective way to handle these errors without over-provisioning capacity?

Accepted Answer

Implement exponential backoff and retry logic in the application.. Option D is correct because implementing exponential backoff with retries handles throttling errors gracefully without over-provisioning. Option A is incorrect because it is costly and inefficient to over-provision. Option B is incorrect because DynamoDB Accelerator (DAX) is a cache, but it does not increase write capacity; it can reduce read load but not write throttling. Option C is incorrect because switching to on-demand may be more cost-effective for spiky traffic, but it is not the most cost-effective if traffic is predictable; the question asks for most cost-effective.

Answer

Increase the provisioned read and write capacity to the peak traffic level.

Answer

Use DynamoDB Accelerator (DAX) to cache frequently accessed items.

Answer

Switch to on-demand capacity mode.

Question 17

A developer accidentally deleted a production RDS for PostgreSQL DB instance. The company has automated backups enabled with a retention period of 7 days. What is the fastest way to restore the database to the state just before the deletion?

Accepted Answer

Create a new DB instance and use point-in-time recovery to the time just before deletion.. Option C is correct. When automated backups are enabled, you can restore a DB instance to any point within the retention period, even after deletion. The deleted instance is retained for the backup retention period. Option A is wrong because point-in-time recovery does not require a manual snapshot. Option B is wrong because a manual snapshot was not taken. Option D is wrong because you cannot recover from the Recycle Bin for RDS instances; RDS does not use the Recycle Bin.

Answer

Recover the instance from the Amazon RDS Recycle Bin.

Answer

Restore from the latest automated snapshot that was taken before deletion.

Answer

Use the AWS DMS to migrate the data from the deleted instance to a new one.

Question 18

A company uses Amazon DynamoDB with provisioned capacity for a critical application. During a traffic spike, the table experiences throttling on write requests. The DBA needs to resolve the issue quickly. Which THREE actions should the DBA take? (Choose THREE.)

Accepted Answer

Implement exponential backoff in the application's write requests.. Option A, Option D, and Option E are correct. Option A increases write capacity immediately. Option D implements exponential backoff to handle throttling. Option E uses DynamoDB Auto Scaling to adjust capacity. Option B is wrong because DAX is for reads, not writes. Option C is wrong because switching to on-demand may cause higher costs and is not a quick fix for the spike.

Answer

Switch the table to on-demand capacity mode.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes.

Question 19

A company uses Amazon ElastiCache for Redis as a caching layer for a database. The cache cluster has one primary and one replica node. During a maintenance event, the primary node fails and the replica is promoted. After promotion, the application experiences increased latency. What should a database specialist do to reduce the impact of future failovers?

Accepted Answer

Enable cluster mode and distribute the cache across multiple shards.. Option D is correct because enabling Multi-AZ with automatic failover ensures a replica in a different AZ is promoted, but the key is to pre-warm the cache or use a larger instance. However, among the options, using a cluster mode with shards distributes load and reduces impact. Option A is incorrect because disabling replica reads doesn't help. Option B is incorrect because increasing replica count without cluster mode may not help. Option C is incorrect because automatic backup does not reduce latency after failover.

Answer

Disable replica reads to avoid stale data.

Answer

Enable automatic backups with a retention period of 35 days.

Answer

Add more replica nodes to the cluster.

Question 20

A database administrator is troubleshooting a backup failure for an Amazon RDS for SQL Server DB instance. The error message states 'Insufficient storage capacity for backup. Free storage space is 0 GB.' The DB instance has 200 GB allocated storage. What is the most likely cause?

Accepted Answer

The DB instance has insufficient free storage space to perform the backup.. Option A is correct because RDS requires free storage for automated backups and logs; insufficient free storage causes backup failure. Option B is wrong because backup retention does not consume storage. Option C is wrong because snapshot storage is separate. Option D is wrong because transaction logs accumulate in allocated storage.

Answer

The DB instance has reached the maximum number of manual snapshots.

Answer

The transaction logs are consuming all allocated storage.

Answer

The backup retention period is set to 0 days, disabling automated backups.