DBS-C01 Practice Test 14 — 15 Questions

Question 1

A company is using Amazon DynamoDB with global tables. The company wants to monitor replication latency between regions. Which CloudWatch metric should the company use?

Accepted Answer

ReplicationLatency. The correct metric is ReplicationLatency, which measures the time elapsed between an update in the source region and its appearance in the replica region for DynamoDB global tables. This metric directly reflects the replication lag between regions, making it the appropriate choice for monitoring cross-region replication performance.

Answer

GlobalTableReplicationLag

Answer

ReplicaLag

Answer

WriteThrottleEvents

Question 2

A company is migrating a 1 TB Microsoft SQL Server database to Amazon RDS for SQL Server using native backup and restore. The DBA has taken a full backup of the source database and uploaded it to an S3 bucket. The DBA then uses the 'aws rds restore-db-instance-from-db-snapshot' CLI command to restore the backup to an RDS instance. The restore fails with an error: 'Could not find the specified backup file in the S3 bucket.' The DBA verifies that the backup file exists in the correct S3 bucket and that the IAM role used by RDS has permissions to access the bucket. What is the most likely cause of the failure?

Accepted Answer

The backup file is not placed in the correct S3 bucket path that includes the account ID prefix.. When restoring a native backup from S3 to RDS, the backup file must be stored in a path that includes the AWS account ID as a prefix (e.g., /123456789012/backup.bak). RDS for SQL Server expects this specific path structure to locate the file. Even if the file exists in the bucket and permissions are correct, a wrong path causes the 'Could not find the specified backup file' error. Option A is wrong because the file extension is not the issue; RDS accepts .bak and .trn files. Option B is wrong because encryption is not required for native restore. Option C is wrong because native restore is a supported feature on RDS for SQL Server; the error is about file location, not configuration.

Answer

The backup file has an incorrect file extension, such as .trn instead of .bak.

Answer

The backup file is not encrypted with AWS KMS.

Answer

The RDS instance is not configured to use native restore.

Question 3

A company's Amazon Redshift cluster is experiencing slow query performance. The cluster has three nodes. The administrator wants to identify if the issue is due to data distribution skew. Which approach should be used?

Accepted Answer

Query the STV_SLICES table to compare disk usage across slices.. The correct approach is to query the STV_SLICES table. STV_SLICES provides disk usage per slice, which can identify data distribution skew. Option A is wrong because STL_QUERY stores query execution times, not distribution. Option B is wrong because STV_WLM_SERVICE_STATE shows current workload management queue state. Option D is wrong because CloudWatch CPUUtilization measures CPU load, not data distribution.

Answer

Examine the STL_QUERY table to analyze query execution times.

Answer

Check the STV_WLM_SERVICE_STATE table to see current queue state.

Answer

Review CloudWatch metrics for CPUUtilization per node.

Question 4

A database specialist is troubleshooting an Amazon RDS for MySQL DB instance that is running out of storage. The instance has automated backups enabled. The specialist needs to free up storage space immediately without losing backup capability. Which action should the specialist take?

Accepted Answer

Delete older automated backups that are no longer needed.. None of the provided options will free up DB instance storage. Automated backups are stored in Amazon S3, not in the instance's allocated storage. To free up instance storage, you would need to increase the allocated storage or delete actual data from the database. Reducing backup retention deletes backups from S3, not instance storage. Manual snapshots are also in S3. Disabling backups stops future backups but does not free existing storage.

Answer

Modify the DB instance to reduce the backup retention period to 0 days.

Answer

Delete manual snapshots from the RDS console.

Answer

Disable automated backups to stop storage consumption.

Question 5

A company is deploying a new microservices application on Amazon ECS. Each microservice needs its own database. Which AWS database service should be used to minimize operational overhead?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is a fully managed NoSQL database that provides single-digit millisecond latency at any scale, making it ideal for microservices that each require their own isolated database. It eliminates operational overhead by handling hardware provisioning, setup, configuration, replication, and patching automatically, with no servers to manage. DynamoDB also supports on-demand capacity mode, which scales automatically based on traffic, perfectly aligning with the dynamic nature of microservices on Amazon ECS.

Answer

Amazon Aurora

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL

Question 6

A company is migrating a 500 GB SQL Server database to Amazon RDS for SQL Server. The database has a large number of stored procedures and triggers. The migration must have minimal downtime. Which approach should be used?

Accepted Answer

Use AWS Database Migration Service (AWS DMS) with full load and ongoing replication. AWS DMS with full load and ongoing replication enables continuous change data capture (CDC) from the source SQL Server database to Amazon RDS for SQL Server, minimizing downtime by keeping the target synchronized until cutover. This approach handles the stored procedures and triggers natively since both source and target are SQL Server, avoiding schema conversion issues.

Answer

Use AWS Schema Conversion Tool (AWS SCT) to convert the schema and AWS DMS for data migration

Answer

Use AWS S3 to store the data and AWS Glue to transform and load into RDS

Answer

Use native SQL Server backup and restore to Amazon RDS

Question 7

A company runs a production Amazon DynamoDB table with on-demand capacity. The table stores session data for a web application. Recently, users have reported occasional slow response times. The operations team notices that the table's ConsumedWriteCapacityUnits metric shows occasional spikes that exceed the provisioned throughput (though on-demand auto-scales), and ThrottledWriteEvents metrics show occasional throttling. The application uses the AWS SDK with default retry logic. The database specialist is asked to investigate. Upon reviewing the table configuration, the specialist finds that the table has a simple primary key (partition key only) and the data access pattern is heavily skewed toward a small number of partition keys. The application writes in batches of 25 items using the BatchWriteItem API. What should the specialist recommend to reduce throttling and improve performance?

Accepted Answer

Implement write sharding by adding a random suffix to the partition key to distribute writes more evenly.. The throttling is caused by a hot partition: the table uses a single partition key, and writes are heavily skewed toward a few keys. By adding a random suffix to the partition key (write sharding), the writes are distributed evenly across all partitions, eliminating hot spots and reducing throttling. The on-demand capacity mode already handles overall throughput, but it cannot prevent throttling on individual partitions when access is skewed.

Answer

Increase the provisioned read capacity units to handle the load.

Answer

Switch the table to provisioned capacity mode and increase write capacity.

Answer

Enable DynamoDB Accelerator (DAX) to cache write operations.

Question 8

A database administrator notices that the free storage space on an Amazon RDS for PostgreSQL DB instance is decreasing rapidly. The instance has automated backups enabled with a retention period of 7 days. Which action should be taken to monitor storage usage and prevent running out of space?

Accepted Answer

Set up a CloudWatch alarm on the FreeStorageSpace metric to notify when space is low.. Setting a CloudWatch alarm on the FreeStorageSpace metric allows proactive monitoring and notification when storage is low. Option A is incorrect because lifecycle policies to move backups to S3 Glacier are not applicable to RDS automated backups; they are managed separately. Option C is incorrect because increasing storage is a reactive measure, not a monitoring action, and may cause downtime. Option D is incorrect because Performance Insights focuses on database performance, not storage tracking.

Answer

Create a lifecycle policy to automatically move old backup files to Amazon S3 Glacier.

Answer

Increase the allocated storage for the DB instance immediately.

Answer

Enable Performance Insights to track storage usage.

Question 9

A company is using Amazon Aurora MySQL-Compatible Edition. The database has frequent deadlocks, and the application team suspects that the isolation level is causing the issue. The current isolation level is REPEATABLE READ. The team wants to reduce deadlocks while maintaining data consistency. Which isolation level should be recommended?

Accepted Answer

READ COMMITTED. (READ COMMITTED) is correct because it reduces locking compared to REPEATABLE READ, which helps minimize deadlocks in high-concurrency environments. In READ COMMITTED, MySQL uses row-level locks only for the duration of the statement, not the entire transaction, reducing the chance of deadlocks. It still provides consistent reads at the statement level, avoiding dirty reads. Option A (READ UNCOMMITTED) is wrong because it allows dirty reads and is not suitable for transactional consistency. Option C (SNAPSHOT ISOLATION) is wrong because it is not supported by MySQL; it is a SQL Server feature. Option D (SERIALIZABLE) is wrong because it increases locking, leading to more deadlocks.

Answer

READ UNCOMMITTED

Answer

SNAPSHOT ISOLATION

Answer

SERIALIZABLE

Question 10

A company is using Amazon ElastiCache for Redis as a caching layer for a web application. The application's response time has increased, and the operations team suspects that cache evictions are occurring frequently. Which ElastiCache metric should be monitored to confirm cache evictions?

Accepted Answer

Evictions. The Evictions metric in Amazon ElastiCache for Redis shows the number of keys evicted due to memory pressure. Option A (CacheHits) is wrong because it indicates successful key retrievals, not evictions. Option B (SwapUsage) is wrong because it shows the amount of swap space used, not eviction count. Option D (CurrItems) is wrong because it shows the current number of items in the cache, not evictions.

Answer

CacheHits

Answer

SwapUsage

Answer

CurrItems

Question 11

A company is using Amazon RDS for SQL Server with Always On Availability Groups. The primary DB instance is in us-east-1, and the secondary is in us-west-2. The application writes to the primary and reads from the secondary. The secondary instance becomes unreachable due to a network issue. What happens to the primary instance?

Accepted Answer

The primary continues to accept read and write operations.. When the secondary DB instance (read replica) becomes unreachable, the primary continues to accept read and write operations normally. The secondary is an asynchronous replica, so its failure does not affect the primary. Option B is wrong because the primary does not stop accepting writes; write operations continue. Option C is wrong because failover is not automatic for asynchronous replicas; manual intervention would be required to promote the secondary. Option D is wrong because the primary remains fully available and does not become read-only.

Answer

The primary stops accepting write operations.

Answer

The primary automatically fails over to the secondary.

Answer

The primary becomes read-only until the secondary is restored.

Question 12

A company is migrating a 5 TB Oracle database to Amazon Aurora MySQL using AWS DMS. The full load completes successfully, but the CDC phase is slow and the target Aurora cluster is consuming high CPU. The DMS instance type is dms.c4.2xlarge. Which change will most likely improve CDC performance?

Accepted Answer

Increase the number of parallel apply threads in the DMS task. Increasing the number of parallel apply threads in the DMS task allows the CDC phase to apply multiple transactions concurrently to the target Aurora cluster, reducing the backlog of changes. The high CPU on the target suggests the apply process is the bottleneck, not the source or network, and DMS's parallel apply threads directly address this by enabling multi-threaded writes, which improves throughput without requiring larger instances.

Answer

Increase the Aurora cluster's max_connections parameter

Answer

Increase the DMS task's target storage allocation

Answer

Change the Aurora cluster to a larger instance class

Question 13

A company is using Amazon RDS for PostgreSQL and wants to implement encryption in transit for all client connections. The security team has identified that some connections are not using SSL. Which TWO actions should the company take to enforce SSL for all connections?

Accepted Answer

Set the 'rds.force_ssl' parameter to '1' in the DB parameter group.. The correct actions to enforce SSL for all connections are A and E. Option A: Setting 'rds.force_ssl' to '1' in the DB parameter group forces the RDS PostgreSQL instance to require SSL for all incoming connections at the server level. Option E: Modifying the 'pg_hba.conf' file to require SSL for all users via 'hostssl' entries ensures that only SSL connections are allowed, complementing the server-side enforcement. Option C is incorrect because associating a custom SSL certificate is not required for enforcing SSL; AWS RDS provides a valid certificate. Option B is a client-side configuration that does not enforce server-side SSL. Option D is client-side and not a server-side enforcement action. Options A and E together provide robust server-side enforcement.

Answer

Install the RDS CA certificate on all client machines.

Answer

Create a new SSL certificate and associate it with the RDS instance.

Answer

Configure the application connection string to use 'sslmode=require'.

Question 14

A company runs an Amazon Aurora MySQL-compatible database cluster. The security team requires that all database credentials be rotated automatically every 30 days. Which combination of AWS services can meet this requirement with minimal operational overhead?

Accepted Answer

Store the password in AWS Secrets Manager and enable automatic rotation with a 30-day interval.. AWS Secrets Manager provides built-in automatic rotation for RDS database credentials. Option A is incorrect because IAM database authentication does not involve password rotation. Option C is incorrect because CloudHSM does not manage password rotation. Option D is incorrect because Systems Manager Parameter Store lacks built-in rotation capabilities for RDS credentials.

Answer

Use IAM database authentication and rotate the IAM user keys every 30 days.

Answer

Use AWS CloudHSM to generate a new password and a Lambda function to update the database.

Answer

Store the password in AWS Systems Manager Parameter Store and use a scheduled Lambda function to update the password.

Question 15

A company is using Amazon Redshift for data warehousing. The operations team notices that queries are running slower than usual. Which Amazon Redshift system view should be used to identify the queries that are consuming the most resources?

Accepted Answer

STL_QUERY. STL_QUERY (option B) is the correct system view because it stores detailed information about query execution, including resource consumption. This allows the operations team to identify which queries are consuming the most resources. The other options are incorrect: SVV_VACUUM_PROGRESS (option A) shows the progress of vacuum operations, not query performance. PG_TABLE_DEF (option C) shows table definitions. STV_TBL_PERM (option D) shows table permissions, not query resource usage.

Answer

SVV_VACUUM_PROGRESS

Answer

PG_TABLE_DEF

Answer

STV_TBL_PERM