DBS-C01 Practice Questions

Question 1

Refer to the exhibit. A company has an S3 bucket with server-side encryption using AWS KMS. The bucket policy allows access to a user, but the user receives 'Access Denied' when trying to download an object. The IAM policy for the user is shown. What is the MOST likely cause?

Accepted Answer

The policy has a condition that limits kms:Decrypt to when the request is made through the S3 service, but the user might be using a different service to access the object (e.g., directly via KMS API).. The IAM policy includes a condition that restricts kms:Decrypt to requests made through the S3 service (via the S3 service principal). If the user attempts to decrypt the object directly using the KMS API (e.g., using AWS CLI with `kms decrypt` command), the condition is not met, resulting in an 'Access Denied' error. Option A is incorrect because MFA is not mentioned in the policy. Option B is incorrect because the KMS key ID is assumed correct as per the scenario. Option C is incorrect because the policy does allow kms:Decrypt, but only conditionally.

Answer

The user does not have MFA enabled.

Answer

The KMS key ID in the policy is incorrect.

Answer

The policy does not allow kms:Decrypt for the S3 bucket.

Question 2

A company's Amazon RDS for Oracle instance is running out of storage space. The database administrator wants to add storage without downtime. Which action should be taken?

Accepted Answer

Use the 'Modify DB Instance' action to increase the allocated storage.. Amazon RDS allows you to modify allocated storage online using the 'Modify DB Instance' action without significant downtime. Option A is wrong because deleting old archived redo logs can free up space temporarily but does not add storage and may impact point-in-time recovery. Option B is wrong because taking a snapshot and restoring to a larger instance requires downtime during the restore process. Option D is wrong because creating a new instance and migrating data involves downtime and is more complex than simply modifying storage.

Answer

Delete old archived redo logs to free up space.

Answer

Take a snapshot and restore to a larger instance.

Answer

Create a new DB instance with larger storage and migrate the data.

Question 3

A company is using Amazon DynamoDB with on-demand capacity mode. The application experiences occasional throttling during traffic spikes. The database administrator wants to implement a solution to reduce throttling. Which THREE actions should the administrator take? (Choose THREE.)

Accepted Answer

Use DynamoDB Accelerator (DAX) to cache frequently accessed items.. Options A, D, and E are correct. Using DynamoDB Accelerator (DAX) caches frequently accessed items, offloading read capacity from the table and reducing read throttling. Implementing exponential backoff and retry logic in the application (option D) and designing the application to handle throttling by retrying with backoff (option E) both ensure that requests are retried gracefully during spikes, reducing the impact of throttling. Option B is incorrect because auto scaling is not applicable to on-demand capacity mode, which scales automatically. Option C is incorrect because switching to provisioned capacity does not inherently reduce throttling; on-demand already handles sudden spikes, but throttling may still occur if the workload exceeds table limits momentarily.

Answer

Enable auto scaling for the table.

Answer

Switch the table to provisioned capacity mode with auto scaling.

Question 4

A company is migrating a PostgreSQL database to Amazon RDS for PostgreSQL. The source database uses custom functions written in PL/Python. What should the company consider?

Accepted Answer

Rewrite the functions in PL/pgSQL or another supported language.. Amazon RDS for PostgreSQL does not support PL/Python because it requires the installation of an untrusted procedural language, which poses security risks in a managed database environment. The correct approach is to rewrite the custom functions in a supported language such as PL/pgSQL, PL/Perl, or PL/Tcl, which are trusted languages available in RDS for PostgreSQL.

Answer

Modify the DB parameter group to enable PL/Python.

Answer

Use RDS Custom for PostgreSQL to install PL/Python.

Answer

Migrate to Aurora PostgreSQL which supports PL/Python.

Question 5

Which TWO AWS services can be used together to migrate an on-premises MySQL database to Amazon Aurora MySQL with minimal downtime? (Select TWO.)

Accepted Answer

AWS Schema Conversion Tool (SCT). AWS Database Migration Service (DMS) can perform continuous replication from an on-premises MySQL source to an Amazon Aurora MySQL target using change data capture (CDC), enabling near-zero downtime. The AWS Schema Conversion Tool (SCT) is used to assess and convert the source schema, including any incompatible objects, to ensure the Aurora target is ready for migration. Together, SCT handles schema transformation while DMS handles the ongoing data replication.

Answer

Amazon Route 53

Answer

AWS CloudFormation

Answer

AWS Global Accelerator

Question 6

Which TWO of the following are advantages of using Amazon Aurora over standard RDS for MySQL?

Accepted Answer

Aurora can deliver up to 5x the throughput of standard MySQL on the same hardware.. Amazon Aurora uses a distributed, SSD-backed storage subsystem that separates compute from storage, enabling it to deliver up to 5x the throughput of standard MySQL running on the same hardware. This performance gain comes from the Aurora storage engine's ability to reduce I/O operations and parallelize writes across multiple storage nodes.

Answer

Aurora automatically fails over to a read replica in case of primary failure.

Answer

Aurora is compatible with PostgreSQL, so you can migrate from SQL Server easily.

Answer

Aurora supports up to 15 read replicas, while RDS for MySQL only supports 5.

Question 7

A company is migrating a 10 TB Oracle database to Amazon Aurora PostgreSQL. The migration uses AWS DMS with CDC. After the full load, the CDC phase is falling behind by several minutes. The source Oracle database generates 500 MB of redo logs per minute. Which action will most likely improve CDC performance?

Accepted Answer

Increase the number of parallel apply threads on the DMS task. Increasing the number of parallel apply threads on the DMS task allows the target Aurora PostgreSQL database to apply changes concurrently, reducing the bottleneck caused by sequential apply. With 500 MB/min of redo logs, the single-threaded default apply cannot keep pace, so parallel apply directly addresses the lag by distributing the load across multiple threads.

Answer

Disable CDC and perform a full load only

Answer

Reduce the batch size in the DMS task settings

Answer

Increase the source Oracle redo log size

Question 8

A company stores financial data in an Amazon Aurora MySQL DB cluster. The security team requires that database audit logs be stored in Amazon CloudWatch Logs and encrypted at rest using a customer-managed KMS key. The database specialist enables audit log publishing to CloudWatch Logs and specifies a KMS key for log encryption. However, the audit logs are not appearing in CloudWatch Logs. What is the most likely cause?

Accepted Answer

The IAM role used for publishing logs does not have the necessary permissions to use the KMS key for CloudWatch Logs.. When publishing database audit logs to CloudWatch Logs with a customer-managed KMS key, the IAM role used by RDS must have explicit permissions for the `kms:Encrypt` and `kms:Decrypt` actions on the KMS key. Without these permissions, RDS cannot encrypt the log stream, and the logs will not appear. Option C correctly identifies this missing permission as the most likely cause.

Answer

The CloudWatch Logs log group does not exist and RDS cannot create it automatically.

Answer

The DB cluster is not configured to export error logs, only audit logs.

Answer

CloudWatch Logs does not support encryption with customer-managed KMS keys for audit logs.

Answer

The audit log parameter is static and requires a DB cluster reboot after modification.

Question 9

A company runs a web application on Amazon EC2 instances behind an Application Load Balancer. The application uses Amazon RDS for MySQL. Recently, the database CPU utilization spikes to 100% during peak hours. The team observes that the spike is caused by a large number of slow queries. They need to identify and resolve the issue with minimal disruption. Which combination of steps should they take? (Choose two.)

Accepted Answer

Enable RDS Performance Insights to identify the slow queries. The correct combination is A and D. Option A: Enabling RDS Performance Insights quickly identifies slow queries and their resource consumption, pinpointing the cause of CPU spikes. Option D: Creating a read replica and directing reporting queries to it offloads read traffic from the primary instance, reducing CPU load during peak hours. Option B is not an identification step and may not address the root cause, while also incurring unnecessary cost. Option C addresses I/O bottlenecks, not CPU spikes from slow queries. Option E helps with connection management but does not identify or directly resolve the slow query issue.

Answer

Upgrade to a larger instance type

Answer

Increase the DB instance storage to improve I/O

Answer

Implement connection pooling using Amazon RDS Proxy

Question 10

Which THREE design patterns are commonly used to optimize DynamoDB performance for write-heavy workloads?

Accepted Answer

Using DynamoDB adaptive capacity to handle unbalanced access patterns.. DynamoDB adaptive capacity automatically isolates heavily accessed partitions, allowing them to consume more throughput without throttling other partitions. This is critical for write-heavy workloads with uneven access patterns, as it prevents hot partitions from degrading overall performance.

Answer

Using sparse indexes on rarely accessed attributes.

Answer

Using global tables to distribute writes across regions.

Question 11

A company uses Amazon RDS for PostgreSQL to store sensor data. Each sensor sends a row every second. The table has grown to 500 GB and queries filtering on a timestamp column are slow even with an index. The team wants to improve query performance while keeping the data online. Which approach should they take?

Accepted Answer

Partition the table by time using PostgreSQL table partitioning. PostgreSQL table partitioning by time (e.g., by day or month) allows the query planner to prune partitions that do not match the timestamp filter, drastically reducing the amount of data scanned. This is the most effective approach for time-series data because it maintains online access and improves query performance without requiring a migration or additional replicas.

Answer

Migrate to Amazon Aurora PostgreSQL and enable parallel query

Answer

Add more indexes on the timestamp column

Answer

Create a read replica and direct queries to the replica

Question 12

A company is migrating a MySQL database from on-premises to Amazon RDS for MySQL. They want to use native MySQL replication to minimize downtime. Which configuration is required in the on-premises MySQL server?

Accepted Answer

Enable binary logging with binlog_format = ROW. Native MySQL replication requires binary logging on the source server to capture all changes. Setting binlog_format = ROW ensures that row-level changes are logged, which is the recommended format for cross-version replication and is required by Amazon RDS for MySQL to support replication from an external source. Without binary logging enabled, the on-premises MySQL server cannot act as a replication master.

Answer

Enable the slow query log

Answer

Enable the audit log

Answer

Enable the error log

Question 13

An e-commerce platform uses Amazon DynamoDB for a shopping cart table with partition key 'user_id' and sort key 'product_id'. The table experiences throttled write requests during flash sales. The access pattern includes reading the entire cart at checkout. Which design change would improve write performance without changing the read pattern?

Accepted Answer

Enable DynamoDB Adaptive Capacity and ensure the table uses on-demand capacity mode. Enabling DynamoDB Adaptive Capacity with on-demand capacity mode automatically scales write capacity to handle traffic spikes during flash sales without requiring manual provisioning. This eliminates throttling while preserving the existing table schema (partition key 'user_id' and sort key 'product_id'), so the read pattern of querying the entire cart by user_id remains unchanged.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes

Answer

Increase the provisioned write capacity units (WCU) to a higher value

Answer

Change the table design to use only partition key 'user_id' and remove the sort key

Question 14

A SysOps administrator is tasked with monitoring the free storage space on all Amazon RDS DB instances. Which AWS service should be used to set up an alarm that sends an email notification when free storage space falls below a threshold?

Accepted Answer

Amazon CloudWatch with an alarm on the FreeStorageSpace metric and an SNS topic.. Amazon CloudWatch provides the `FreeStorageSpace` metric for RDS DB instances, which reports the amount of available storage in bytes. You can create a CloudWatch alarm on this metric and configure it to send a notification via an Amazon SNS topic when the value falls below a specified threshold, enabling proactive monitoring of storage capacity.

Answer

AWS CloudTrail to monitor storage events.

Answer

AWS Config to track storage configuration changes.

Answer

Amazon Inspector to check for storage vulnerabilities.

Question 15

A company uses Amazon DynamoDB with fine-grained access control based on user identity. The IAM policy for a user includes a condition that restricts access to items where the 'department' attribute equals 'engineering'. However, the user is receiving an 'AccessDeniedException' when trying to query items. What is the most likely cause?

Accepted Answer

The 'department' attribute is not the partition key of the table.. Fine-grained access control in DynamoDB uses IAM policy conditions with the 'dynamodb:LeadingKeys' or 'dynamodb:Attributes' condition keys. The 'department' attribute must be the partition key of the table for 'LeadingKeys' to work. If 'department' is not the partition key, the condition cannot be evaluated for the query. Option A is possible but less likely if the user is using the correct role. Option C is wrong because DynamoDB does not require SSL for all operations. Option D is wrong because Condition check is exactly how it works.

Answer

The user is not using the correct IAM role.

Answer

The DynamoDB table is not configured to require SSL.

Answer

The IAM policy is missing a 'Condition' block.

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