DBS-C01 Mock Exam 79 — 25 Questions

Question 1

A database specialist sees the above error log entries from an Amazon RDS for MySQL DB instance. Which action should be taken to resolve the issue?

Accepted Answer

Restore the DB instance from the latest automated snapshot.. The error log entries indicate corruption in the InnoDB tablespace, likely due to a crash or hardware failure. Restoring from the latest automated snapshot is the correct action because it provides a consistent, point-in-time recovery of the entire database, including all table structures and data, without relying on potentially corrupted files. This approach ensures data integrity and avoids further damage that could occur from attempting repairs on a corrupted instance.

Answer

Increase the allocated storage for the DB instance.

Answer

Reboot the DB instance to clear the error.

Answer

Run the mysqlcheck command to repair the corrupted tables.

Question 2

A company runs a financial application on Amazon RDS for PostgreSQL that requires point-in-time recovery (PITR) with a recovery point objective (RPO) of 1 second and recovery time objective (RTO) of 5 minutes. Which configuration meets these requirements at the lowest cost?

Accepted Answer

Multi-AZ RDS with synchronous standby.. Multi-AZ RDS for PostgreSQL with synchronous standby replication provides automatic failover to a standby in a different Availability Zone, enabling an RTO of typically 1–2 minutes, well within the 5-minute requirement. Automated backups and transaction logs allow PITR with an RPO of 1 second by restoring to any point within the retention period, and the synchronous standby ensures zero data loss during failover, meeting the strict RPO at the lowest cost for this high-availability need.

Answer

Single-AZ RDS with automated backups and manual snapshot restore.

Answer

Single-AZ RDS with a read replica and promote on failure.

Answer

Single-AZ RDS with cross-region snapshot copy.

Question 3

A company needs to store time-series data from IoT sensors. Each sensor sends a reading every minute. The data is rarely accessed after 30 days. The query pattern is to retrieve all readings for a specific sensor within a time range. Which AWS database is most cost-effective?

Accepted Answer

Amazon Timestream. Amazon Timestream is purpose-built for time-series data, offering automatic tiered storage (in-memory for recent data and magnetic for historical data) and built-in time-series functions. For IoT sensors sending readings every minute with rare access after 30 days, Timestream's cost-effective storage tiering and efficient querying for a specific sensor within a time range make it the most suitable and economical choice.

Answer

Amazon Redshift

Answer

Amazon DynamoDB with Time-to-Live (TTL)

Answer

Amazon RDS for PostgreSQL with partitioning

Question 4

A company is migrating a 500 GB Oracle database to Amazon RDS for Oracle. They need to validate the migration and ensure data consistency. Which TWO methods should they use?

Accepted Answer

Use AWS DMS data validation feature.. AWS DMS data validation (Option B) is a built-in feature that automatically compares source and target records by computing checksums on each row, ensuring end-to-end data consistency without manual effort. Comparing row counts and checksums (Option D) is a standard manual validation technique that provides a reliable, independent verification of data completeness and integrity. Together, these two methods cover both automated and manual validation, which is critical for a 500 GB migration where manual inspection of every row is impractical.

Answer

Use Amazon S3 inventory reports on the exported data.

Answer

Run random SELECT queries on a subset of tables.

Answer

Use Amazon CloudWatch Logs to compare database logs.

Question 5

A company runs an Amazon ElastiCache for Redis cluster as a caching layer for a high-traffic web application. The cluster has one primary and two replica nodes. Recently, the application experienced increased latency. Monitoring shows that the CPU utilization of the primary node is consistently above 80%, while replicas are below 40%. The application uses the cluster mode disabled. The operations team needs to reduce the CPU load on the primary node. Which solution should they implement?

Accepted Answer

Configure the application to use read replicas for read queries by using the reader endpoint.. Offloading read traffic to replicas reduces CPU load on the primary node. Configuring the application to use the reader endpoint for read queries distributes read operations across replicas, lowering the primary's CPU utilization. Option A (DAX) is unrelated to ElastiCache Redis. Option B (vertical scaling) may help but is often more expensive and does not leverage replicas. Option D (adding replicas) does not reduce primary CPU unless reads are directed to them.

Answer

Implement a read-through cache pattern using DynamoDB Accelerator (DAX).

Answer

Upgrade the primary node to a larger instance type.

Answer

Add more replica nodes to the cluster.

Question 6

A company is migrating a 1 TB SQL Server database to Amazon RDS for SQL Server. They want to use the native backup and restore feature. What must they do first?

Accepted Answer

Upload the backup file to an Amazon S3 bucket.. To use the native backup and restore feature for migrating a SQL Server database to Amazon RDS, you must first upload the backup file to an Amazon S3 bucket. RDS for SQL Server supports restoring from backup files stored in S3 via the `RESTORE DATABASE` command, using the `FROM URL` option that references the S3 bucket. This is the only supported method for native restore, as RDS does not allow direct file system access or FTP transfers.

Answer

Store the backup file on an EBS volume attached to the RDS instance.

Answer

Use FTP to transfer the backup file directly to the RDS instance.

Answer

Use the AWS Management Console to upload the backup file to the RDS instance.

Question 7

A company needs to securely store and manage the master password for their Amazon RDS for PostgreSQL instance. Which AWS service is purpose-built for managing secrets with automatic rotation?

Accepted Answer

AWS Secrets Manager. AWS Secrets Manager is designed for secret management with built-in rotation. Option A is wrong because KMS is for encryption keys, not secret management. Option C is wrong because IAM is for identity and access management, not secret storage. Option D is wrong because CloudHSM provides hardware security modules but not secret rotation.

Answer

AWS Key Management Service (KMS)

Answer

AWS Identity and Access Management (IAM)

Answer

AWS CloudHSM

Question 8

Which TWO AWS services can be used to centrally manage database credentials and automate rotation for Amazon RDS? (Choose two.)

Accepted Answer

AWS Secrets Manager. Options A and D are correct. AWS Secrets Manager provides native automated rotation for RDS credentials, while AWS Systems Manager Parameter Store (SecureString) can centrally store encrypted credentials and support automated rotation when combined with a custom AWS Lambda function. Both services allow centralized management of database credentials, and with additional configuration, both can automate rotation. Option B (AWS KMS) is incorrect because KMS manages encryption keys, not secrets. Option C (IAM database authentication) is incorrect because it eliminates the need for stored credentials but does not centrally manage or rotate them. Option E (AWS CloudHSM) is incorrect because it provides hardware security modules for key storage, not secret management.

Answer

AWS Key Management Service (KMS)

Answer

IAM database authentication

Answer

AWS CloudHSM

Question 9

A company is using Amazon DynamoDB with auto scaling enabled. The table has a provisioned read capacity of 10,000 RCU and write capacity of 5,000 WCU. Auto scaling target utilization is 70%. The table experiences a sudden spike in read traffic, reaching 12,000 RCU. The table throttles some requests. Which THREE actions should the company take to prevent future throttling?

Accepted Answer

Implement exponential backoff in the application to retry throttled requests.. Implementing exponential backoff with jitter helps handle throttled requests gracefully by retrying after increasing delays, reducing further load on the table. Option B is correct because increasing the maximum read capacity in the auto scaling configuration allows the table to scale up further (beyond 10,000 RCU) during traffic spikes, preventing throttling. Option E is correct because enabling DynamoDB Accelerator (DAX) caches read requests, offloading the table and reducing the read load that can cause throttling. Option C is wrong because decreasing the target utilization would cause auto scaling to trigger earlier, but it does not increase the maximum capacity; the table would still be limited to the max capacity set, and the spike might exceed it. Option D is wrong because the issue is read traffic, not write capacity, so increasing write capacity does not address read throttling.

Answer

Decrease the auto scaling target utilization to 50% to scale out earlier.

Answer

Increase the write capacity to 10,000 WCU.

Question 10

A database specialist is troubleshooting an Amazon DynamoDB table that is experiencing high throttling on write requests. The table has on-demand capacity and uses a composite primary key (partition key and sort key). Which TWO actions should the specialist take to identify and resolve the issue?

Accepted Answer

Examine the partition key value distribution to identify hot partitions. High throttling on write requests often results from uneven partition key distribution, creating hot partitions. Option A is correct: examining the partition key value distribution helps identify hot partitions. Option E is correct: reviewing CloudWatch metrics for WriteThrottleEvents and ConsumedWriteCapacityUnits helps identify throttled write requests and analyze capacity usage. Options B, C, and D are incorrect: DAX is a read cache and does not affect write throughput; changing to provisioned capacity or increasing read capacity units does not resolve write throttling caused by hot partitions.

Answer

Implement DynamoDB Accelerator (DAX) to offload read traffic

Answer

Change the table to provisioned capacity mode

Answer

Increase the read capacity units on the table

Question 11

Refer to the exhibit. An IAM policy is attached to a user who needs to deploy an RDS MySQL instance. After creating the instance, the user tries to modify it to enable deletion protection, but the action fails. What is the most likely reason?

Accepted Answer

The user does not have permission to enable deletion protection.. The IAM policy shown in the exhibit grants `rds:CreateDBInstance` but does not include `rds:ModifyDBInstance` or the specific action required to enable deletion protection (`rds:ModifyDBInstance` with the `DeletionProtection` parameter). Enabling deletion protection is a modification action, not part of the creation process, so the user lacks the necessary IAM permission for that operation.

Answer

The user does not have permission to describe instances.

Answer

The resource ARN is not specified in the policy.

Answer

The user does not have permission to create the instance.

Question 12

A company is using Amazon ElastiCache for Redis as a caching layer for a web application. Users report that some cached data is missing, causing slower responses. Which ElastiCache feature should be checked first to understand key evictions?

Accepted Answer

Evictions metric in CloudWatch. The Evictions metric in CloudWatch directly shows the number of keys evicted from ElastiCache for Redis due to memory pressure. This is the first metric to check when cached data is missing, as evictions indicate that the cache is full and items are being removed to make space for new ones. Option A (ReplicationLag) measures replication delay between primary and replica nodes, not related to evictions. Option B (CPUUtilization) shows CPU usage but does not indicate evictions. Option D (CacheHits) shows how often requested keys are found in the cache, but does not show evictions. Therefore, option C is correct.

Answer

ReplicationLag metric

Answer

CPUUtilization metric

Answer

CacheHits metric in CloudWatch

Question 13

A company has an Amazon RDS for SQL Server DB instance that stores financial data. The security team requires that the data be encrypted at rest using a customer-managed key stored in AWS KMS. Additionally, they want to ensure that the key cannot be deleted without authorization. What should be done?

Accepted Answer

Create a customer-managed KMS key, enable key rotation, and set a deletion protection policy.. Creating a customer-managed KMS key allows you to control key rotation and deletion protection, meeting the security requirements. Option B is wrong because using the default KMS key does not provide a customer-managed key. Option C is wrong because AWS CloudHSM is not directly used for RDS encryption at rest; KMS is the required service. Option D is wrong because AWS CloudTrail only logs actions but does not prevent key deletion.

Answer

Enable encryption on the RDS instance and use the default KMS key.

Answer

Use AWS CloudHSM to generate and store the encryption key, and associate it with the RDS instance.

Answer

Enable AWS CloudTrail to log key deletion attempts.

Question 14

A company has an Aurora MySQL cluster with three instances. The current writer instance is 'mycluster-instance-1'. The company wants to failover to 'mycluster-instance-2' for maintenance. What is the most direct way to achieve this?

Accepted Answer

Use the AWS CLI: aws rds failover-db-cluster --db-cluster-identifier mycluster --target-db-instance-identifier mycluster-instance-2. The AWS CLI command `aws rds failover-db-cluster` with the `--target-db-instance-identifier` parameter allows you to explicitly specify which Aurora replica should become the new writer instance. This is the most direct and supported method to initiate a controlled failover to 'mycluster-instance-2' without rebooting the current writer or manually modifying endpoints.

Answer

Change the cluster's endpoint to point to instance-2.

Answer

Modify 'mycluster-instance-2' to promote it to writer.

Answer

Reboot 'mycluster-instance-1' to trigger a failover.

Question 15

An IAM policy is attached to a user who needs to restore an Amazon RDS DB instance from a DB snapshot. The user attempts to restore and receives an 'Access Denied' error. Which missing permission is MOST likely causing the failure?

Accepted Answer

rds:CreateDBInstance. To restore an Amazon RDS DB instance from a DB snapshot, the user must have the `rds:CreateDBInstance` permission. This is because the restore operation internally calls the CreateDBInstance API to create a new DB instance from the specified snapshot. Without this permission, the request fails with an 'Access Denied' error, even if the user has permissions to describe snapshots or instances.

Answer

rds:DescribeDBSnapshots

Answer

rds:DescribeDBInstances

Answer

rds:CreateDBSubnetGroup

Question 16

Refer to the exhibit. A developer is trying to query the ProductCatalog table using the 'Id' attribute. The query returns no results even though the developer knows data was inserted. What is the MOST likely cause?

Accepted Answer

The table contains no items. The table shows ItemCount: 0, indicating no items exist. Even though data was inserted, if the write operation failed or was directed to a different table, the query returns no results. Option B is incorrect because provisioned throughput issues would cause throttling errors, not zero items. Option C is incorrect because the attribute definition exists (Id is defined). Option D is incorrect because the table status is ACTIVE as shown.

Answer

The provisioned throughput is exceeded

Answer

The attribute definition is missing the 'Id' attribute

Answer

The table is not in ACTIVE status

Question 17

Refer to the exhibit. An IAM policy is attached to a role used by an application running on Amazon EC2. The application needs to read items from a DynamoDB table named 'MyTable' and create manual snapshots of an RDS instance. What is the issue with the policy?

Accepted Answer

The policy does not grant any DynamoDB read actions (e.g., GetItem, Query, Scan) required for the application.. The policy only grants 'PutItem' and 'DeleteItem' actions on the DynamoDB table, but the application needs to read items (e.g., 'GetItem' or 'Scan'). The missing DynamoDB read actions are the primary issue. Option B is incorrect because 'DescribeDBInstances' on all resources is not inherently too permissive for this use case; the key issue is the missing read permissions. Option C is incorrect because using 'Resource': '*' for DynamoDB is acceptable for read actions if the table ARN is not specified; it is not a policy structure problem. Option D is incorrect because 'CreateDBSnapshot' on '*' is allowed, but the policy correctly scopes RDS actions to 'Resource': '*' which includes all DB instances; the critical flaw remains the missing DynamoDB read actions.

Answer

The policy allows 'DescribeDBInstances' on all resources, which is too permissive.

Answer

The policy uses 'Resource': '*' for DynamoDB, which should be the table ARN.

Answer

The policy grants 'CreateDBSnapshot' on all resources, which is insufficient; it should be scoped to the specific DB instance.

Question 18

A company runs an analytics platform that queries billions of rows of sales data. Queries are complex and involve aggregations across multiple dimensions. The data is updated in bulk daily. Which service should be used as the primary data store?

Accepted Answer

Amazon Redshift. Amazon Redshift is the correct choice because it is a fully managed, petabyte-scale data warehouse optimized for complex analytical queries involving aggregations across multiple dimensions. Its columnar storage, massively parallel processing (MPP) architecture, and ability to handle bulk daily updates via COPY commands or INSERT operations make it ideal for querying billions of rows of sales data.

Answer

Amazon DynamoDB

Answer

Amazon Athena

Answer

Amazon RDS for MySQL

Question 19

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The migration uses AWS DMS with ongoing replication (CDC). Which TWO tasks must be completed before starting the migration?

Accepted Answer

Enable supplemental logging in the Oracle source database. AWS DMS requires supplemental logging to be enabled on the Oracle source database for ongoing replication (CDC). Supplemental logging ensures that the redo logs contain sufficient information (e.g., primary key, unique key, or all column values) to reconstruct the changes for DMS to capture and apply to the target. Without it, DMS cannot generate the necessary log-based change data for CDC.

Answer

Configure DMS to use only full load without CDC

Answer

Disable archive logging on the Oracle source

Answer

Enable binary logging on the Oracle source

Question 20

A company is designing a global e-commerce platform using Amazon DynamoDB. The platform must support strong consistency for inventory updates and eventual consistency for product catalog reads. Which TWO design patterns should the company implement to meet these consistency requirements?

Accepted Answer

Configure DynamoDB Accelerator (DAX) for product catalog queries with eventual consistency.. DynamoDB Accelerator (DAX) is an in-memory cache that can be configured to return eventually consistent results for read-heavy workloads like product catalog queries, reducing read latency and cost while meeting the eventual consistency requirement. Option E is correct because DynamoDB global tables replicate data across regions, and using strongly consistent reads for inventory queries ensures that the most recent write is returned, which is critical for inventory accuracy.

Answer

Use Amazon ElastiCache for Redis to cache inventory data with strong consistency.

Answer

Use DynamoDB transactions for all inventory operations.

Answer

Use DynamoDB Streams to replicate inventory changes to a separate table for reads.