DBS-C01 Practice Test 22 — 15 Questions

Question 1

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?

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

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 2

A media company stores video metadata in Amazon DynamoDB. Each record has a partition key of video_id and a sort key of uploaded_timestamp. The application frequently queries videos by genre and upload date. The access pattern is read-heavy with occasional writes. The table is provisioned with 3000 RCUs and 1000 WCUs. The company notices that queries by genre are slow and consume many RCUs. Which design change should be made to optimize for this workload?

Accepted Answer

Create a global secondary index (GSI) with genre as partition key and uploaded_timestamp as sort key.. Creating a Global Secondary Index (GSI) with genre as the partition key and uploaded_timestamp as the sort key allows efficient querying by genre and date without scanning the entire table. This directly supports the access pattern, reducing RCU consumption by using index key lookups instead of full table scans. The GSI is ideal for read-heavy workloads with occasional writes, as it offloads query traffic from the main table.

Answer

Use DynamoDB Accelerator (DAX) to cache query results.

Answer

Create a local secondary index (LSI) with genre as sort key and uploaded_timestamp as partition key.

Answer

Increase the provisioned RCUs to 6000.

Question 3

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database is 2 TB in size. The company wants to minimize downtime during the migration. Which AWS service should be used to perform an online migration with minimal downtime?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) supports ongoing replication to minimize downtime. Snowball is for offline data transfer. S3 is not a migration service. Direct Connect provides a dedicated network connection but is not a migration service itself.

Answer

AWS Direct Connect

Answer

AWS Snowball

Answer

Amazon S3

Question 4

A database specialist is configuring an Amazon Aurora PostgreSQL cluster for a production workload. The specialist must ensure that the cluster can recover from an Availability Zone failure and that read traffic is distributed across multiple replicas without application changes. Which two actions should the specialist take? (Choose two.)

Accepted Answer

Create Aurora Replicas in multiple Availability Zones within the cluster's Region.. Aurora provides storage replication across three AZs automatically, but compute-level fault tolerance requires Aurora Replicas placed in multiple AZs, since a replica in a surviving AZ can be promoted. The reader endpoint gives applications one DNS name that load-balances connections across replicas, distributing read traffic without code changes. Together these actions satisfy both the AZ resilience and read distribution requirements.

Answer

Increase the cluster's backup retention period to 35 days to improve Availability Zone resilience.

Answer

Configure a custom endpoint that includes only the writer instance for read traffic.

Answer

Enable Multi-AZ on the Aurora cluster to create a synchronous standby instance.

Question 5

Refer to the exhibit. An IAM policy statement allows creating manual snapshots for an RDS instance. A database administrator is unable to create a snapshot from the AWS Management Console. The error message indicates insufficient permissions. What is the likely cause?

Accepted Answer

The policy does not include necessary read actions (e.g., 'DescribeDBInstances', 'DescribeDBSnapshots') that the console uses.. The AWS Management Console does not call only the mutating API (CreateDBSnapshot); it first calls read/describe APIs such as DescribeDBInstances and DescribeDBSnapshots to render the page and validate the instance. If the IAM policy grants only CreateDBSnapshot, the console's prerequisite calls fail with AccessDenied, producing the 'insufficient permissions' error even though the create action itself is allowed. Adding the describe permissions resolves the issue.

Answer

The condition key 'aws:RequestedRegion' is misspelled.

Answer

The resource ARN is incorrect; it should include the snapshot ARN.

Answer

The condition uses 'StringEquals' but should use 'StringLike' for region matching.

Question 6

A database specialist sees the above error in the application logs for an Amazon RDS for MySQL DB instance. The application is a web server running on an EC2 instance. What is the most likely cause?

Accepted Answer

The database connection timed out due to inactivity or network connectivity issues.. The error message in the application logs indicates a connection timeout, which occurs when the client (EC2 web server) cannot establish or maintain a TCP connection to the RDS MySQL DB instance within the configured timeout period. This is most commonly caused by network connectivity issues (e.g., security group rules, NACLs, route tables, or VPC misconfigurations) or prolonged inactivity that triggers the MySQL `wait_timeout` or `interactive_timeout` setting, causing the server to close the connection. Option C directly addresses this scenario, while the other options produce different error codes or symptoms.

Answer

The database user password has expired.

Answer

A user attempted to execute an invalid SQL query.

Answer

The database instance has run out of disk space.

Question 7

A company is deploying a new web application and needs a fully managed relational database with automatic failover and read replicas. Which AWS service should they choose?

Accepted Answer

Amazon RDS for MySQL with Multi-AZ deployment. Amazon RDS for MySQL with Multi-AZ deployment provides a fully managed relational database service that automatically provisions and maintains a synchronous standby replica in a different Availability Zone. In the event of a failure, Amazon RDS automatically fails over to the standby, ensuring high availability. Additionally, RDS for MySQL supports read replicas for offloading read traffic, which meets the requirement for both automatic failover and read replicas.

Answer

Amazon DynamoDB

Answer

Amazon EC2 with self-managed MySQL

Answer

Amazon Redshift

Question 8

A company is using Amazon RDS for Oracle with a very large database (10 TB). They need to migrate to Amazon Aurora PostgreSQL with minimal downtime. The source database is heavily used with constant writes. Which migration strategy is most appropriate?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication to migrate from Oracle to Aurora PostgreSQL.. AWS DMS with ongoing replication (change data capture) is the most appropriate strategy for migrating a heavily written 10 TB Oracle database to Aurora PostgreSQL with minimal downtime. DMS can perform a full load of the existing data and then continuously replicate changes from Oracle's redo logs to Aurora PostgreSQL, allowing the source to remain fully operational until a brief cutover window. This approach minimizes downtime compared to offline export/import methods and is natively supported by AWS.

Answer

Export the Oracle database using expdp and import into Aurora PostgreSQL using pg_restore.

Answer

Create a read replica of the RDS Oracle instance and promote it to an Aurora PostgreSQL instance.

Answer

Use Oracle GoldenGate to replicate data to an Aurora PostgreSQL instance.

Question 9

A database administrator runs the above AWS CLI command. What is the purpose of the command?

Accepted Answer

Retrieve average number of database connections for mydb.. The AWS CLI command `aws cloudwatch get-metric-statistics` with the namespace `AWS/RDS`, metric name `DatabaseConnections`, and statistic `Average` retrieves the average number of database connections for the specified DB instance `mydb` over the given time period. The `--metric-name DatabaseConnections` parameter explicitly targets the connection count metric, making option B correct.

Answer

Retrieve average free storage space for mydb.

Answer

Retrieve average CPU utilization for mydb.

Answer

Retrieve average write latency for mydb.

Question 10

A database specialist is responsible for an Amazon Neptune cluster. The operations team reports that some Gremlin queries are timing out. The specialist needs to monitor the cluster to identify slow queries. Which AWS service or feature should the specialist use to capture and analyze the query performance?

Accepted Answer

Neptune's slow query logs in CloudWatch Logs.. Neptune's slow query logs, when enabled and published to CloudWatch Logs, capture Gremlin queries that exceed a configured threshold, including execution time and query text. This is the designed feature for monitoring slow queries. CloudWatch Logs allows searching and analyzing these logs. Other options like audit logs, X-Ray, or CloudTrail do not provide the detailed query performance metrics needed to identify and troubleshoot slow Gremlin queries.

Answer

AWS CloudTrail with Neptune data events.

Answer

AWS X-Ray with Neptune tracing.

Answer

Amazon CloudWatch Logs with Neptune audit logs.

Question 11

A company runs an Amazon Aurora MySQL database cluster with one writer and one reader instance. The application experiences intermittent connection timeouts during peak traffic. The DB cluster parameter group has 'connect_timeout' set to 5 seconds. What should a database specialist recommend to reduce connection timeouts?

Accepted Answer

Enable RDS Proxy for the cluster.. RDS Proxy pools and reuses database connections, absorbing the connection churn and bursty spikes that cause timeouts when many application connections compete for a limited number of backend connections. By multiplexing client connections onto a smaller pool of established database connections, it reduces the connection establishment overhead and timeouts during peak traffic.

Answer

Add additional reader instances to distribute the load.

Answer

Increase the 'connect_timeout' parameter to 10 seconds.

Answer

Enable IAM database authentication and require TLS.

Question 12

A developer reports that an application using Amazon DynamoDB is experiencing high latency during peak hours. The table has a provisioned capacity of 500 read capacity units (RCUs) and 500 write capacity units (WCUs). The application uses eventually consistent reads and the table is about 50 GB. The developer notices throttled write requests in CloudWatch. Which action would most effectively reduce write throttling?

Accepted Answer

Increase the provisioned write capacity for the table.. The developer reports throttled write requests, which directly indicates that the provisioned write capacity (500 WCUs) is insufficient to handle the peak write traffic. Increasing the provisioned write capacity for the table is the most direct and effective action to eliminate write throttling, as it raises the limit on write operations per second. Option C is correct because it addresses the root cause—write capacity exhaustion—without introducing unnecessary components or changing read behavior.

Answer

Enable DynamoDB Accelerator (DAX) for the table.

Answer

Create a global secondary index on the table.

Answer

Switch from eventually consistent reads to strongly consistent reads.

Question 13

A developer needs to allow an application running on an EC2 instance to read and write data to a DynamoDB table named 'Orders'. The EC2 instance is configured with an IAM role. Which IAM policy should be attached to the role?

Accepted Answer

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": [ "dynamodb:GetItem", "dynamodb:PutItem" ], "Resource": "arn:aws:dynamodb:us-east-1:123456789012:table/Orders" } ] }. The policy grants exactly the required DynamoDB actions (GetItem and PutItem) on the specific 'Orders' table, following the principle of least privilege. Option A is incorrect because it grants full DynamoDB access to all tables, which is overly permissive. Option B is incorrect because it grants EC2 actions, not DynamoDB actions. Option D is incorrect because it grants S3 actions instead of DynamoDB actions.

Answer

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": "dynamodb:*", "Resource": "*" } ] }

Answer

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": "ec2:*", "Resource": "*" } ] }

Answer

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": "s3:*", "Resource": "arn:aws:s3:::example-bucket/*" } ] }

Question 14

A database administrator is troubleshooting an issue where an Amazon RDS for PostgreSQL DB instance is not allowing connections. The administrator checks the security group and network ACLs, and they are correctly configured. What is the next step to diagnose the issue?

Accepted Answer

Review the DB instance error logs in Amazon CloudWatch. When security groups and network ACLs are correctly configured but an RDS for PostgreSQL instance still refuses connections, the next diagnostic step is to review the DB instance error logs in Amazon CloudWatch. These logs often reveal the root cause, such as the instance being in a failed state, a parameter misconfiguration, or an internal error preventing the database from accepting connections.

Answer

Reboot the DB instance

Answer

Modify the DB instance's parameter group

Answer

Create a DB snapshot

Question 15

A company is building a document management system where each document can have multiple attributes (tags) that need to be queried efficiently. The workload is write-heavy with occasional reads. Which database is best suited?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the best choice for a write-heavy, document management system with tag-based queries because it is a fully managed NoSQL key-value and document database that delivers single-digit millisecond performance at any scale. Its flexible schema allows each document to have multiple attributes (tags) without predefined schemas, and its secondary indexes (LSI/GSI) enable efficient querying on those tags. DynamoDB's auto-scaling and provisioned throughput are designed to handle high write volumes, while occasional reads benefit from its consistent low-latency access.

Answer

Amazon QLDB

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL