DBS-C01 Practice Test 16 — 15 Questions

Question 1

A company uses Amazon DynamoDB to store IoT sensor data. Each sensor writes a record every second, and the application needs to query the last 24 hours of data for a specific sensor. The query must be very fast. Which table design and query pattern will minimize cost and latency?

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

Accepted Answer

Use a composite primary key: partition key = sensor ID, sort key = timestamp. Using a composite primary key with partition key = sensor ID and sort key = timestamp allows DynamoDB to efficiently query all items for a specific sensor in a single partition, using the Query API with a sort key condition on timestamp. This design ensures fast, targeted reads without scanning, minimizing read capacity units and latency.

Answer

Use a simple primary key (sensor ID) and scan the table filtering by timestamp

Answer

Use a composite primary key: partition key = timestamp, sort key = sensor ID

Answer

Use a simple primary key (sensor ID) and a global secondary index on timestamp

Question 2

A company wants to restrict access to an Amazon DynamoDB table so that only requests from a specific VPC endpoint are allowed. Which policy should be attached to the table?

Accepted Answer

A VPC endpoint policy that allows only the specific VPC endpoint to access the DynamoDB table.. A VPC endpoint policy attached to the VPC endpoint can restrict which DynamoDB tables are accessible through that endpoint. Option A is incorrect because security groups apply to EC2 instances and other network interfaces, not to DynamoDB tables. Option B is incorrect because while IAM policies can include conditions to restrict access based on source VPC, they are attached to IAM users or roles, not directly to the DynamoDB table. Option D is incorrect because bucket policies are used for Amazon S3, not DynamoDB.

Answer

A security group rule that allows traffic only from the VPC endpoint.

Answer

An IAM policy that denies access unless the request comes from the specific VPC.

Answer

An S3 bucket policy that references the DynamoDB table.

Question 3

A snapshot of an Amazon RDS DB instance is shown in the exhibit. What does the output indicate?

Accepted Answer

The snapshot is encrypted and the encryption process is complete.. The snapshot is encrypted (Encrypted: true) and the status is 'encrypted', indicating that the encryption process is complete. Option A is incorrect because the snapshot exists and is not in progress. Option C is incorrect because the snapshot is indeed encrypted. Option D is incorrect because the status shows 'encrypted', not 'encrypting'.

Answer

The snapshot creation is still in progress.

Answer

The snapshot is not encrypted.

Answer

The snapshot is in the process of being encrypted.

Question 4

A company uses Amazon DynamoDB for a time-series IoT workload. Each device sends a data point every minute. The primary key consists of device_id (partition key) and timestamp (sort key). The company wants to efficiently retrieve the latest 10 data points for a specific device. Which query design is most efficient?

Accepted Answer

Query the table with ScanIndexForward=false and Limit=10.. Query with ScanIndexForward=false retrieves items in descending order by the sort key (timestamp), and Limit=10 stops after the first 10 items, which are the most recent 10 data points for the given device_id. This is the most efficient design as it reads only the 10 items needed, leveraging the DynamoDB local secondary index or table's sort key order without any post-processing.

Answer

Use GetItem on the device_id partition key with the maximum timestamp.

Answer

Query the table with ScanIndexForward=true and Limit=10, then reverse the result set.

Answer

Scan the entire table and filter by device_id, then sort by timestamp.

Question 5

A company needs to store and analyze log data from thousands of servers. The logs are timestamped and rarely updated. Queries are mostly time-range aggregations. Which database service is best suited for this workload?

Accepted Answer

Amazon CloudWatch Logs. Amazon CloudWatch Logs is purpose-built for ingesting, storing, and analyzing timestamped log data from distributed sources. It supports real-time and historical time-range aggregations via Logs Insights, which uses a query language optimized for pattern matching and aggregation over time windows. The service automatically handles high-throughput ingestion from thousands of servers and is cost-effective for append-only, rarely updated log data.

Answer

Amazon ElastiCache for Redis

Answer

Amazon DynamoDB

Answer

Amazon RDS for PostgreSQL

Question 6

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database contains sensitive data that must be encrypted at rest using a customer-managed KMS key. The company also needs to ensure that the database is automatically patched by AWS. Which DB instance configuration should be used?

Accepted Answer

Multi-AZ, encryption at rest enabled with a customer-managed KMS key, auto minor version upgrade enabled.. The requirements are encryption at rest with a customer-managed KMS key and automatic patching via auto minor version upgrade. Both B (Multi-AZ) and C (Single-AZ) meet these requirements. A fails because auto minor version upgrade is disabled. D fails because it uses an AWS-managed KMS key, not a customer-managed key. High availability is not a requirement in the stem, so both B and C are correct.

Answer

Single-AZ, encryption at rest enabled with a customer-managed KMS key, auto minor version upgrade disabled.

Answer

Multi-AZ, encryption at rest enabled with an AWS-managed KMS key, auto minor version upgrade enabled.

Question 7

An administrator runs the CLI command shown in the exhibit and sees the output. The DB instance 'mydb' is currently running MySQL 5.7.22. What does the output indicate?

Accepted Answer

The DB instance has a pending minor version upgrade to 5.7.23. The output shows 'Pending maintenance: Yes' with 'Minor version upgrade to 5.7.23' listed. This indicates that the DB instance has a pending minor version upgrade that will be applied during the next maintenance window. The CLI command 'aws rds describe-db-instances --db-instance-identifier mydb' returns this information when a minor version upgrade is scheduled but not yet applied.

Answer

The master user password has been changed

Answer

The DB instance has failed to apply modifications

Answer

The DB instance is using a custom DB parameter group

Question 8

A developer accidentally deleted a critical table from an Amazon RDS for MySQL DB instance. Automated backups are enabled with a retention period of 7 days. The deletion occurred 3 hours ago. Which action can restore the table with minimal data loss?

Accepted Answer

Perform a point-in-time restore to a time just before the deletion.. Amazon RDS point-in-time recovery (PITR) allows restoring a DB instance to any second within the backup retention period, enabling recovery to just before the table deletion, minimizing data loss. Option B is incorrect because AWS DMS is a migration tool, not a recovery mechanism for deleted data. Option C is incorrect because restoring from the latest automated snapshot would lose all changes made after that snapshot, including the 3 hours of data before deletion. Option D is incorrect because while MySQL binary logs can be used for point-in-time recovery, RDS manages this through its automated PITR feature; manually replaying binary logs is not a supported operation in RDS.

Answer

Use AWS Database Migration Service to replicate the table from another source.

Answer

Restore the DB instance from the latest automated snapshot.

Answer

Use the MySQL binary log to replay transactions up to the deletion.

Question 9

A gaming company wants to store player profiles and game state. The data is accessed via a REST API and must be highly available with single-digit millisecond latency. The schema is simple and may evolve over time. Which database should they use?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the correct 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 high-availability gaming workloads. Its schema-less design allows the player profile and game state schema to evolve over time without downtime or complex migrations, and it integrates seamlessly with REST APIs via AWS SDKs or API Gateway.

Answer

Amazon S3

Answer

Amazon RDS for PostgreSQL

Answer

Amazon Redshift

Question 10

An e-learning platform uses Amazon Aurora MySQL for its database. The application runs reporting queries that scan large portions of the database, causing high CPU utilization on the primary instance. The primary instance is a db.r5.2xlarge with 64 GB memory. The reporting queries are not time-sensitive but need to return results within 5 minutes. The operations team wants to reduce the impact on the primary instance without increasing costs significantly. Which action should be taken?

Accepted Answer

Create an Aurora Replica and configure the reporting application to connect to the replica endpoint. To create an Aurora Replica and direct reporting traffic to it. This offloads the heavy reporting queries from the primary instance, reducing CPU impact without significant cost increase. Aurora Replicas share the same storage and are cost-effective for read-heavy workloads.

Answer

Modify the DB cluster parameter group to enable result set caching

Answer

Use Amazon ElastiCache to cache the reporting results

Answer

Increase the primary instance to db.r5.4xlarge

Question 11

Match each AWS database feature to its description.

Accepted Answer

Multi-AZ: Provides high availability by automatically replicating data to a standby instance in a different Availability Zone.. Multi-AZ is for high availability and failover; Read Replicas offload read traffic; Auto Scaling adjusts capacity; Point-in-Time Recovery enables granular restores. Common confusions involve swapping Multi-AZ and Read Replicas definitions.

Answer

Multi-AZ: Allows you to offload read traffic from the primary database.

Answer

Read Replicas: Provides high availability by automatically replicating data to a standby instance.

Question 12

Refer to the exhibit. A DBA deploys this CloudFormation stack. After creation, the DBA needs to enable deletion protection for the DB instance. Which modification to the template would accomplish this?

Accepted Answer

Add 'DeletionProtection': true to the Properties.. Adding 'DeletionProtection': true to the Properties of the AWS::RDS::DBInstance resource enables deletion protection for that DB instance. Option B is incorrect because 'DeletionPolicy: Retain' is a CloudFormation resource-level attribute that retains the resource when the stack is deleted, but it does not prevent deletion of the resource outside of CloudFormation. Option C is incorrect because 'PreventRDSDeletion' is not a valid property for RDS. Option D is incorrect because the correct syntax is 'DeletionProtection': true, not 'Enabled'.

Answer

Add 'DeletionPolicy: Retain' to the resource.

Answer

Add 'PreventRDSDeletion: true' to the Properties.

Answer

Add 'DeletionProtection': 'Enabled' to the Properties.

Question 13

A startup is building a social media application with a news feed feature. The feed must be personalized and updated in real-time as users post. Which AWS database service is best suited for this workload?

Accepted Answer

Amazon ElastiCache for Redis with sorted sets and pub/sub. Amazon ElastiCache for Redis is the best choice because it provides in-memory data structures like sorted sets for ranking and scoring personalized feeds, and pub/sub for real-time notifications when new posts are published. This combination enables low-latency, real-time feed updates without the overhead of disk-based storage, making it ideal for a social media news feed that must be both personalized and updated in real-time.

Answer

Amazon DynamoDB with Global Secondary Indexes

Answer

Amazon S3 with Select and Glacier

Answer

Amazon RDS for PostgreSQL with read replicas

Question 14

A company needs to migrate a 10 TB SQL Server database from on-premises to Amazon RDS for SQL Server with minimal downtime. The database is heavily used with frequent write operations. Which migration strategy should be used?

Accepted Answer

Use AWS DMS with ongoing replication from the on-premises database to RDS until cutover.. AWS DMS with ongoing replication (change data capture) allows a full load of the 10 TB database followed by continuous replication of write operations from the on-premises SQL Server to Amazon RDS for SQL Server. This minimizes downtime by keeping the target database synchronized until the cutover window, where only a brief pause is needed to apply final changes and switch traffic.

Answer

Use native SQL Server backup and restore to Amazon S3, then restore to RDS.

Answer

Export the database to CSV files, upload to S3, and use the COPY command in RDS.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema, then use AWS DMS for full load.

Question 15

Refer to the exhibit. A DBA is troubleshooting a performance issue on an RDS for MySQL DB instance. The DBA runs the AWS CLI command shown. Based on the output, which of the following is a potential performance bottleneck?

Accepted Answer

The storage type is gp2, which may have limited IOPS performance.. The instance uses gp2 storage, which has burstable IOPS. If the burst balance is depleted, performance can degrade. The engine version is recent, Multi-AZ is not enabled, but that affects availability, not necessarily performance. DB instance status is available so no issue there.

Answer

The DB instance is not Multi-AZ, causing failover delay.

Answer

The DB instance status is 'available', meaning it is not accepting connections.

Answer

The engine version 8.0.27 has a known performance bug.