DBS-C01 Practice Test 16 — 15 Questions

Question 1

A company is building a social network application that needs to store user profiles, friend relationships, and a feed of posts. The feed queries are complex, involving graph traversals (e.g., friends of friends). Which database is best suited for the relationship data?

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

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for storing and querying highly connected data. It supports both property graph and RDF models, and it uses graph traversal languages like Gremlin and SPARQL, making it ideal for complex friend-of-friend queries and social network relationship data.

Answer

Amazon DynamoDB

Answer

Amazon RDS for MySQL

Answer

Amazon ElastiCache for Redis

Question 2

Refer to the exhibit. A developer runs the command against an RDS MySQL instance. The application team reports that the database is experiencing high read latency during peak hours. The database is not currently in Multi-AZ. What is the MOST cost-effective way to reduce read latency?

Accepted Answer

Create a read replica in the same region.. Creating a read replica in the same region offloads read traffic from the primary RDS MySQL instance, reducing read latency during peak hours without incurring the cost of a larger instance or a full Aurora migration. Read replicas are asynchronous and can serve SELECT queries, providing a cost-effective scaling solution for read-heavy workloads.

Answer

Enable Multi-AZ to distribute reads to the standby.

Answer

Upgrade the instance to db.r5.2xlarge.

Answer

Migrate to Aurora MySQL with a read replica.

Question 3

A company is using an Amazon DynamoDB table with a global table configuration across two AWS regions. The security team wants to ensure that all data is encrypted in transit between the regions. What should the team do?

Accepted Answer

No additional action is required; DynamoDB global tables encrypt all replication traffic in transit by default.. DynamoDB global tables automatically encrypt all replication traffic between regions using TLS. No additional configuration is needed to ensure encryption in transit for cross-region replication. This is a built-in security feature of global tables.

Answer

Configure an Internet gateway in each region and enforce HTTPS for all traffic.

Answer

Use AWS CloudFront to route traffic between the regions with SSL/TLS termination.

Answer

Set up a VPC peering connection between the two regions and route DynamoDB traffic through it.

Question 4

Arrange the steps to perform a point-in-time recovery (PITR) for an Amazon RDS for MySQL DB instance in the correct order.

Accepted Answer

Identify the desired recovery time, then initiate the restore operation specifying the source DB instance and target time, then monitor the restore progress until the new DB instance is available, then verify the data in the restored instance.. PITR restores the database to a specific time within the backup retention window by selecting the restore option and specifying the time.

Answer

Identify the desired recovery time, then monitor the restore progress, then initiate the restore, then verify the data.

Answer

Initiate the restore operation, then identify the desired recovery time, then monitor the restore progress, then verify the data.

Answer

Identify the desired recovery time, then initiate the restore, then verify the data, then monitor the restore progress.

Question 5

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 6

A startup is building a social media analytics platform. The workload is write-heavy, with millions of events per day containing user actions (likes, shares, comments). The data model is simple: each event is a JSON document with a timestamp, user ID, and action type. Queries are primarily aggregations over time (e.g., count of likes per hour) and require low-latency responses for dashboards. The team wants to minimize operational overhead and cost. Which database service is most appropriate?

Accepted Answer

Amazon Timestream, a purpose-built time-series database.. Amazon Timestream is a serverless, purpose-built time-series database that automatically scales to ingest millions of events per day and provides built-in time-series functions for aggregations like count per hour. It requires no infrastructure management, offers low-latency queries for dashboards, and uses a cost-effective tiered storage model (memory and magnetic) that automatically moves older data to cheaper storage. Its native time-series capabilities make it ideal for this write-heavy, time-based aggregation workload.

Answer

Amazon ElastiCache for Redis to store aggregated counts.

Answer

Amazon RDS for PostgreSQL with TimescaleDB extension.

Answer

Amazon DynamoDB with global secondary indexes on timestamp and action type.

Question 7

A company is migrating its on-premises Oracle database to Amazon RDS for Oracle. The database contains sensitive data that must be encrypted at rest and in transit. The security team also requires that the encryption keys be rotated every year. The DBA has enabled encryption at rest using a customer-managed KMS key and SSL/TLS for in-transit encryption. What additional step is needed to meet the key rotation requirement?

Accepted Answer

Enable automatic KMS key rotation for the customer-managed key.. For a customer-managed KMS key, you can enable automatic key rotation, which rotates the key material every year (or a custom period). This meets the requirement without manual intervention. The RDS instance continues to use the same key ID, but the underlying key material is rotated, and old data remains decryptable.

Answer

Manually create a new KMS key every year and update the RDS instance to use the new key.

Answer

Configure the RDS option group to rotate the encryption key.

Answer

Use an AWS CloudHSM key and configure automatic rotation.

Question 8

A company has an Amazon DynamoDB table that stores IoT sensor data. The table has a partition key of device_id and a sort key of timestamp. The team wants to efficiently retrieve the latest reading for each device. Which query pattern should be used?

Accepted Answer

Query with ScanIndexForward=false and Limit=1. Setting ScanIndexForward=false on a Query returns items in descending sort-key order. By querying with the device_id as the partition key and limiting results to 1, you retrieve the most recent timestamp for that device efficiently without scanning the entire table.

Answer

Scan with FilterExpression to get the latest timestamp for each device

Answer

Query with ScanIndexForward=true and Limit=1

Answer

GetItem with the device_id and timestamp values

Question 9

Refer to the exhibit. You run the command and get the output shown. The database is an RDS for MySQL instance. You need to connect to it from an EC2 instance in the same VPC. Which connection string should be used?

Accepted Answer

mysql -h mydb.123456789012.us-east-1.rds.amazonaws.com -P 3306 -u admin -p. The command uses the MySQL client (`mysql`) with the correct fully qualified domain name (FQDN) of the RDS instance, which includes the AWS account ID and region, and the default MySQL port 3306. The `-u admin -p` flags specify the master username and prompt for a password, which is the standard way to connect to an RDS for MySQL instance from an EC2 instance in the same VPC.

Answer

psql -h mydb.123456789012.us-east-1.rds.amazonaws.com -p 5432 -U admin

Answer

mysql -h mydb.us-east-1.rds.amazonaws.com -P 3306 -u admin -p

Answer

mysql -h mydb.123456789012.us-east-1.rds.amazonaws.com -P 5432 -u admin -p

Question 10

A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. They want to use the AWS DMS for the migration. Which THREE resources need to be created in the AWS account?

Accepted Answer

DMS target endpoint pointing to Aurora PostgreSQL.. AWS DMS migrations require a replication instance (D) to run the migration tasks, so a DMS replication instance must be created in the account. You also need a source endpoint (E) that points to the existing PostgreSQL database, which defines the connection and credentials for reading data. Finally, a target endpoint (C) pointing to the Aurora PostgreSQL cluster is required so DMS knows where to load the migrated data. An Application Load Balancer (A) is not part of DMS architecture, and a CloudFormation stack (B) is an optional provisioning method, not a required DMS resource.

Answer

Application Load Balancer for the replication instance.

Answer

AWS CloudFormation stack to provision resources.

Question 11

A gaming company wants to store player profiles and game state data with low-latency access for millions of concurrent users. The data is accessed via a REST API and requires high scalability with minimal operational overhead. Which database service is MOST suitable?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the most suitable choice because it is a fully managed NoSQL key-value and document database that delivers single-digit millisecond latency at any scale, making it ideal for storing player profiles and game state data for millions of concurrent users. It supports high throughput with auto-scaling, integrates seamlessly with REST APIs via AWS SDKs, and requires minimal operational overhead due to its serverless nature.

Answer

Amazon RDS for MySQL with read replicas

Answer

Amazon Neptune

Answer

Amazon ElastiCache for Redis

Question 12

A company uses Amazon DynamoDB with provisioned capacity for a gaming application. During a new game launch, write traffic spikes to 2x the provisioned write capacity for 30 minutes. Some writes are throttled. The company wants to handle these predictable spikes without manual intervention. What is the MOST cost-effective solution?

Accepted Answer

Enable DynamoDB auto scaling with a target utilization of 70%.. DynamoDB auto scaling automatically adjusts provisioned capacity based on actual usage, handling predictable spikes without manual intervention while minimizing cost by scaling down when demand drops. Option A is wrong because permanently doubling capacity leads to wasted resources and higher costs. Option B is wrong because on-demand mode can be more expensive for predictable workloads with consistent baseline traffic. Option D is wrong because SQS buffers writes but does not directly address DynamoDB write throttling; it adds latency and complexity without solving the capacity issue.

Answer

Increase the provisioned write capacity to 2x the baseline permanently.

Answer

Change the table to on-demand capacity mode.

Answer

Use Amazon SQS to buffer writes and process them later.

Question 13

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 supports increasing allocated storage on an existing DB instance through the Modify DB Instance action, and this operation is performed online without downtime. The storage increase takes effect without requiring a restart or migration, making it the correct answer for adding space without downtime.

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 14

A company is using Amazon Neptune to run graph queries. The cluster has one writer and two reader instances. After a major version upgrade, the query performance degrades for complex traversal queries. The database specialist suspects that the query optimizer is not using indexes effectively. Which action should the specialist take to identify the issue?

Accepted Answer

Enable the Neptune explain plan feature and review the output.. The Neptune explain plan feature provides detailed information about how a query is executed, including which indexes are used, the traversal order, and where performance bottlenecks occur. By enabling and reviewing the explain output, the specialist can directly verify whether the query optimizer is using indexes effectively and identify specific steps that cause degradation. This is the most direct and appropriate action for diagnosing query plan issues after a version upgrade.

Answer

Drop and recreate all indexes to ensure they are up to date.

Answer

Add more reader instances to distribute the query load.

Answer

Check the CloudWatch metrics for CPU utilization and query latency.

Question 15

A company is migrating a 3 TB Oracle database to Amazon RDS for Oracle. The migration uses AWS DMS with ongoing replication. The source database is actively used by applications. After the initial full load, the target RDS instance is in sync. However, during the ongoing replication phase, the replication task fails with an error: 'ORA-1555: snapshot too old.' The DMS task has been set up with a source endpoint that uses the 'Oracle TNS' connection method. The company needs to resolve the issue without stopping the source database. Which action should be taken?

Accepted Answer

Increase the undo retention period in the source Oracle database.. The ORA-1555 error indicates that undo data is overwritten before DMS can read it. Increasing undo retention ensures the snapshot data is available longer. Reducing batch size would not address the undo issue. Increasing logging frequency does not affect undo. Using a different connection method does not solve the underlying undo retention problem.

Answer

Change the source endpoint to use the 'Oracle SID' connection method.

Answer

Decrease the batch size of the DMS task.

Answer

Increase the frequency of the DMS task's log mining.