DBS-C01 Practice Test 26 — 15 Questions

Question 1

Refer to the exhibit. A company is creating an Aurora MySQL cluster using the AWS CLI. The command fails with an error. The company has a default KMS key but the command specifies a customer-managed KMS key. What is the most likely cause of the failure?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The IAM user does not have permission to use the specified KMS key. The most likely cause of the failure is that the IAM user does not have the required permissions to use the specified customer-managed KMS key. When you specify a KMS key in the `--kms-key-id` parameter for an Aurora MySQL cluster, the IAM user must have `kms:CreateGrant`, `kms:Decrypt`, and `kms:Encrypt` permissions on that key. If the user lacks these permissions, the command fails even if the key exists and is in the correct region.

Answer

The --kms-key-id parameter is not supported for aurora-mysql engine

Answer

The KMS key does not exist

Answer

The KMS key is in a different region

Question 2

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. During the migration, the database administrator notices that the CPU utilization on the RDS instance is consistently above 90% during peak hours, even though the on-premises server had similar specifications. The application queries are mostly SELECT statements with occasional DML. The RDS instance is db.r5.large with 500 GB of General Purpose SSD (gp2) storage. Which change would most likely reduce CPU utilization?

Accepted Answer

Upgrade to a larger instance type, such as db.r5.xlarge.. The db.r5.large instance type has 2 vCPUs and 16 GiB of memory. Sustained CPU utilization above 90% during peak hours indicates that the instance is compute-bound for the workload. Upgrading to db.r5.xlarge (4 vCPUs, 32 GiB memory) doubles the available CPU capacity, directly reducing CPU utilization for the same query load. The on-premises server had similar specifications, but RDS instances may have different CPU architectures or hypervisor overhead, making the larger instance the most direct fix.

Answer

Create a read replica and redirect all SELECT queries to the replica.

Answer

Enable Multi-AZ to offload CPU to the standby instance.

Answer

Increase the allocated storage to 1 TB to improve I/O performance.

Question 3

Which THREE factors should be considered when choosing between Amazon RDS and Amazon DynamoDB for a new application? (Choose 3.)

Accepted Answer

Access patterns (predictable vs. ad-hoc). Amazon RDS is a relational database service that excels at complex queries involving joins and aggregations, while DynamoDB is a NoSQL key-value and document database optimized for predictable, high-scale access patterns. The choice between them hinges on whether the application requires relational features (RDS) or can tolerate denormalized schemas for low-latency, horizontal scaling (DynamoDB). Option C is correct because DynamoDB is designed for ad-hoc, single-key lookups and simple queries, whereas RDS supports complex, ad-hoc SQL queries with joins.

Answer

Cost of storage

Answer

Need for encryption at rest

Question 4

Which TWO options are valid methods for migrating an on-premises SQL Server database to Amazon RDS for SQL Server with minimal downtime? (Choose TWO.)

Accepted Answer

Use AWS DMS with ongoing replication from the source.. AWS DMS with ongoing replication (change data capture, CDC) is a valid method for migrating to Amazon RDS for SQL Server with minimal downtime because it allows you to perform a full load of the database and then continuously replicate incremental changes from the source until you cut over. This keeps the target nearly in sync, reducing the downtime window to seconds or minutes.

Answer

Use AWS CloudEndure to replicate the entire server.

Answer

Copy the database files to Amazon S3 and restore to RDS.

Answer

Use SQL Server Import/Export Wizard.

Question 5

An IAM policy is attached to a user who is deploying an RDS database. The user attempts to create a DB instance named 'my-database' using the AWS CLI. Which statement is true?

Accepted Answer

The user can create the DB instance. The IAM policy explicitly allows the `rds:CreateDBInstance` action for the resource `arn:aws:rds:us-east-1:123456789012:db:my-database`. The Deny statement only applies to actions not listed in the Allow statement, but since the specific action and resource match the Allow, the user is permitted to create the DB instance. AWS IAM evaluates policies with an explicit Allow overriding an implicit Deny, and the Deny here does not block the allowed action.

Answer

The user cannot create the DB instance because the Deny statement applies to all actions

Answer

The user cannot create the DB instance because the resource ARN does not exist yet

Answer

The user cannot create the DB instance because of an error in the policy

Question 6

A company is running an Amazon RDS for MySQL DB instance in a VPC. The security team requires that all connections to the database use SSL/TLS. Which combination of steps should be taken to enforce this? (Choose two.)

Accepted Answer

Require database users to connect using the --ssl-ca parameter with the RDS certificate.. To enforce SSL on RDS MySQL, you set the rds.force_ssl parameter to 1 in the DB parameter group and require users to connect using the --ssl-ca option. The option group is for features like Oracle TDE, not SSL enforcement. Security group rules control network access, not encryption enforcement. Option E is unnecessary if you set the parameter.

Answer

Create a new DB subnet group that isolates the DB instance in a private subnet without internet access.

Answer

Update the security group for the DB instance to deny inbound traffic on port 3306 from sources that do not have SSL.

Answer

Modify the DB option group associated with the DB instance, enabling the SSL option.

Question 7

A company has an Amazon RDS for SQL Server DB instance with Multi-AZ deployment. During a recent failover test, the application experienced a longer downtime than expected. The application uses a single connection string. What change should be made to reduce failover downtime?

Accepted Answer

Use a custom DNS CNAME record pointing to the RDS endpoint.. Using a custom DNS CNAME record that points to the RDS endpoint allows the application to control the DNS Time-To-Live (TTL) value independently. By setting a low TTL (e.g., 5 seconds) on the CNAME, the application's DNS resolver will refresh the IP address more quickly after a failover, reducing the time the application spends trying to connect to the old, unreachable primary instance. This minimizes downtime because the application can resolve the new primary's IP address sooner, rather than relying on the default RDS endpoint's TTL, which is typically set to 60 seconds and cannot be modified.

Answer

Implement connection pooling in the application.

Answer

Set the DNS TTL to a higher value.

Answer

Configure the application to use the RDS instance ID instead of endpoint.

Question 8

An administrator runs the above AWS CLI command to create an RDS MySQL instance. The command completes successfully. What is the status of the new DB instance immediately after the command returns?

Accepted Answer

creating. When you run the AWS CLI command to create an RDS MySQL instance, the command returns immediately after the API call is accepted and the instance enters the 'creating' state. The instance is not yet available because provisioning, configuring, and booting the database engine takes several minutes. The 'creating' status indicates that AWS is actively setting up the DB instance, and it will transition to 'available' only after the entire creation process completes.

Answer

available

Answer

stopped

Answer

deleting

Question 9

A social media company uses Amazon DynamoDB to store user posts. The table has a partition key of 'user_id' and a sort key of 'post_timestamp'. Each item is about 10 KB. The application needs to retrieve all posts for a given user within a date range. The company recently added a new feature that allows users to 'like' posts, and they store the like count as an attribute in the post item. The like count is updated frequently. The application experiences high write throttling on the table. The table has 1000 WCUs provisioned. The write pattern is bursty. Which design change would MOST effectively reduce write throttling?

Accepted Answer

Add a random suffix to the user_id partition key to distribute writes across multiple partitions.. The write throttling is caused by a 'hot partition' — all writes for a given user_id go to the same partition, and the bursty write pattern (e.g., many likes on a single post) exceeds the partition's 1,000 WCU limit (1,000 write capacity units per partition). Adding a random suffix to the user_id partition key distributes writes across multiple partitions, effectively increasing the write throughput for that logical user's data. This is a common design pattern for DynamoDB to handle high-traffic items without increasing provisioned capacity.

Answer

Increase the WCUs to 5000.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes.

Answer

Create a Global Secondary Index (GSI) on the like count attribute.

Question 10

A company is designing a disaster recovery plan for an Amazon DynamoDB table that stores critical session data. The table is provisioned with on-demand capacity. The recovery objective is to have the data available in another AWS Region within 15 minutes of a regional outage. Which design should they choose?

Accepted Answer

Use DynamoDB Global Tables to replicate data across Regions.. DynamoDB Global Tables provide multi-Region, fully replicated tables with automatic conflict resolution, enabling active-active replication that meets the 15-minute recovery objective without manual intervention. Global Tables replicate data across Regions in sub-second latency, ensuring data availability within the required RTO during a regional outage.

Answer

Use DynamoDB on-demand backups and restore to another Region.

Answer

Use DynamoDB Streams to replicate data to a table in another Region via AWS Lambda.

Answer

Create cross-Region Read Replicas for DynamoDB.

Question 11

A gaming company uses Amazon DynamoDB to store player profiles. The table has partition key 'player_id' and sort key 'game_id'. During a new game launch, write traffic to a subset of players (influencers) spikes, causing throttling. The table uses on-demand capacity. Which solution resolves the hot key issue?

Accepted Answer

Add a random suffix to the partition key for the hot players to distribute writes. Adding a random suffix to the partition key for hot players distributes the write traffic across multiple partitions, preventing any single partition from being overwhelmed. DynamoDB's on-demand capacity mode automatically scales to handle traffic spikes, but it cannot resolve a hot key issue where all writes target the same partition key. By diversifying the partition key, writes are spread across partitions, allowing DynamoDB to utilize its full throughput capacity.

Answer

Increase the maximum read capacity units in the on-demand settings

Answer

Switch to provisioned capacity mode and increase write capacity units

Answer

Enable DynamoDB Accelerator (DAX) to cache writes

Question 12

A company is migrating a 5 TB Oracle database to Amazon RDS for Oracle. The database contains large BFILEs stored in a file system. The company needs to migrate the data with minimal downtime and ensure the BFILEs are migrated. Which THREE steps should the company take?

Accepted Answer

Use AWS SCT to convert any incompatible schema objects.. The correct steps for migrating a 5 TB Oracle database with BFILEs to Amazon RDS for Oracle with minimal downtime are: (B) Use AWS Schema Conversion Tool (SCT) to identify and convert incompatible schema objects, ensuring the target schema is ready. (C) Upload the BFILEs to Amazon S3 and use Oracle Directory objects to reference them in the target database, as BFILEs reference files stored outside the database. (E) Use AWS Database Migration Service (DMS) with the Oracle source endpoint configured to include the BFILE directory path, enabling DMS to migrate the BFILEs during the continuous replication phase, minimizing downtime. Option A (replacing BFILEs with BLOBs) is unnecessary because DMS handles BFILEs natively, and such a change would increase complexity and downtime. Option D (using CloudEndure Migration) is designed for server-level migration, not database-level, and would not be appropriate for this database migration.

Answer

Replace BFILEs with BLOBs in the source database before migration.

Answer

Use AWS CloudEndure Migration to replicate the entire server.

Question 13

A database specialist is troubleshooting an Amazon RDS for SQL Server instance that is experiencing high CPU utilization. The instance has multiple databases. Which TWO actions should the specialist take to identify the cause?

Accepted Answer

Use Performance Insights to identify top SQL queries. Options B and E are correct because Performance Insights helps identify top SQL queries causing high CPU, and Enhanced Monitoring provides OS-level metrics (like CPU utilization per database process) to pinpoint the source. Option A is wrong: read replicas offload read traffic but do not diagnose CPU issues. Option C is wrong: increasing instance size is a remediation, not a diagnostic step. Option D is wrong: changing to a burstable instance class is also a remediation, not diagnostic.

Answer

Create a read replica to offload read traffic

Answer

Increase the instance size to handle the load

Answer

Modify the DB instance class to a burstable type

Question 14

Match each AWS service to its primary purpose.

Accepted Answer

RDS: Managed relational database service supporting multiple engines. These are core AWS database services with distinct use cases. Common confusions include mixing up Redshift (data warehouse) with ElastiCache (in-memory cache) and Neptune (graph) with DocumentDB (document).

Answer

Redshift: Fully managed in-memory caching service

Answer

ElastiCache: Fully managed petabyte-scale data warehouse

Answer

Neptune: Fully managed document database

Question 15

A company is designing a database for an e-commerce application that needs to store product catalog data. The data is highly structured with relationships between products, categories, and suppliers. The application requires ACID transactions to maintain data integrity when updating inventory. The company expects moderate read and write traffic. Which AWS database service is MOST suitable for this workload?

Accepted Answer

Amazon RDS for MySQL. Amazon RDS for MySQL is the most suitable choice because it provides a fully managed relational database that supports ACID transactions, which are essential for maintaining data integrity during inventory updates. The highly structured nature of product catalog data with relationships between products, categories, and suppliers maps naturally to MySQL's relational model with foreign keys and joins. RDS for MySQL handles moderate read/write traffic efficiently and offers features like Multi-AZ for high availability and read replicas for scaling reads.

Answer

Amazon ElastiCache for Redis

Answer

Amazon Neptune

Answer

Amazon DynamoDB