DBS-C01 Practice Test 2 — 10 Questions

Question 1

A social media startup is selecting a database for user profiles with a flexible schema and high write throughput. The application is built on Node.js and requires low-latency access. Which database should they choose?

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

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the correct choice because it is a fully managed NoSQL key-value and document database that offers flexible schema (schemaless), single-digit millisecond latency at any scale, and is designed for high write throughput. It integrates natively with Node.js via the AWS SDK and supports auto-scaling to handle unpredictable write loads, making it ideal for a social media startup's user profile store.

Answer

Amazon Aurora

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Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Question 2

A company needs to store and query time-series data from IoT devices. The data arrives in high volume and requires efficient range queries over time. Which database is most appropriate?

Accepted Answer

Amazon Timestream. Amazon Timestream is a purpose-built time-series database that automatically scales to handle high-volume IoT data and is optimized for efficient range queries over time. It separates storage into a memory store for recent data and a magnetic store for historical data, enabling fast queries across time ranges with built-in time-series functions.

Answer

Amazon RDS for MySQL

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Amazon DynamoDB

Answer

Amazon Redshift

Question 3

A company is designing a database for a mobile application that requires offline synchronization. Users should be able to read and write data while offline, and changes should sync when connectivity is restored. Which AWS service supports this pattern?

Accepted Answer

AWS AppSync with Amazon DynamoDB. AWS AppSync with Amazon DynamoDB is correct because AppSync provides managed GraphQL APIs that support offline data synchronization via its client SDKs. When a mobile app is offline, mutations are queued locally and automatically replayed against DynamoDB once connectivity is restored, using a conflict resolution mechanism (e.g., last-writer-wins or custom resolvers) to merge changes.

Answer

Amazon RDS Proxy

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Amazon S3 Transfer Acceleration

Answer

Amazon Cognito

Question 4

A security engineer is designing a VPC with an RDS instance. The database must not be accessible from the internet, but EC2 instances in a private subnet must connect. Which security group configuration is MOST secure?

Accepted Answer

Set the RDS security group inbound rule to allow traffic from the EC2 security group on port 3306.. The most secure because it uses a security group reference instead of a CIDR block. By referencing the EC2 security group as the source in the RDS security group inbound rule, only instances associated with that specific security group can communicate with the database on port 3306. This approach adheres to the principle of least privilege and automatically scales as instances are added or removed from the EC2 security group, without needing to update CIDR ranges.

Answer

Set the RDS security group inbound rule to allow traffic from the VPC CIDR on port 3306.

Answer

Set the RDS security group inbound rule to allow traffic from 0.0.0.0/0 on port 3306.

Answer

Set the RDS security group inbound rule to allow traffic from the private subnet CIDR on port 3306.

Question 5

A company is running a critical application on Amazon RDS for Oracle. They need to ensure high availability with automatic failover in case of a database failure. The database size is 500 GB. Which solution should they implement?

Accepted Answer

Enable Multi-AZ deployment. Multi-AZ deployment for Amazon RDS for Oracle provides synchronous replication to a standby instance in a different Availability Zone, with automatic failover in the event of a database failure. This ensures high availability without manual intervention, meeting the requirement for automatic failover for a 500 GB Oracle database.

Answer

Create a cross-Region read replica

Answer

Migrate to Amazon DynamoDB Global Tables

Answer

Take regular snapshots and restore in a different Availability Zone

Question 6

A company is using Amazon DynamoDB with on-demand capacity. The application experiences increased latency during peak hours. The DynamoDB table receives about 5,000 writes per second and 10,000 reads per second. The read latency is high, but write latency is acceptable. What should the company do to reduce read latency?

Accepted Answer

Enable DynamoDB Accelerator (DAX) for the table.. DynamoDB Accelerator (DAX) is a fully managed, highly available, in-memory cache that significantly reduces read latency for DynamoDB tables, especially for repeated reads. DAX allows you to offload read traffic from the table and serve read requests from the cache, reducing the load on the table and improving response times. Option A is wrong because DynamoDB Streams is used to capture changes to items in the table, not to cache data or offload read traffic. Option B is wrong because DynamoDB does not support read replicas; DAX is the caching solution for reads. Option D is wrong because switching to provisioned capacity and enabling auto scaling would help with scaling write capacity but does not directly address high read latency; DAX is specifically designed for in-memory caching to improve read performance.

Answer

Enable DynamoDB Streams to offload read traffic.

Answer

Create a read replica of the DynamoDB table.

Answer

Switch to provisioned capacity and enable auto scaling.

Question 7

A financial services company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database has a high volume of write transactions and requires minimal downtime during migration. Which AWS service or feature should be used to replicate data continuously to the target RDS instance during the migration?

Accepted Answer

AWS Database Migration Service (AWS DMS) with ongoing replication. AWS Database Migration Service (AWS DMS) with ongoing replication (change data capture, CDC) is the correct choice because it continuously captures and applies changes from the source Oracle database to the target Amazon RDS for Oracle instance, enabling near-zero downtime during migration. This is achieved by using Oracle's redo logs to stream transactions in real time, which meets the high write volume and minimal downtime requirements.

Answer

Amazon RDS Read Replica

Answer

Amazon RDS Multi-AZ deployment

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AWS Schema Conversion Tool (AWS SCT)

Question 8

A company is designing a database for an e-commerce platform that requires high availability and automatic failover with minimal downtime. The application performs both OLTP and read-heavy analytics. Which AWS database service should be used?

Accepted Answer

Amazon Aurora. Amazon Aurora is the correct choice because it combines the high availability and automatic failover of a relational database with the performance needed for both OLTP and read-heavy analytics. Aurora provides six-way replication across three Availability Zones, automatic failover in under 30 seconds, and supports up to 15 low-latency read replicas that can offload analytics queries without impacting write performance.

Answer

Amazon DynamoDB

Answer

Amazon RDS for MySQL

Answer

Amazon Redshift

Question 9

A startup is building a social media application that needs to store user profiles, posts, comments, and likes. The data is highly interconnected, and the team wants to query relationships efficiently, such as 'find all friends of a user who liked a post'. Which database service is best suited for this workload?

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for highly interconnected data. It supports property graph and RDF models, enabling efficient traversal of relationships such as 'find all friends of a user who liked a post' using Gremlin or SPARQL queries. This makes it the ideal choice for social media applications requiring real-time relationship queries.

Answer

Amazon ElastiCache for Redis

Answer

Amazon DynamoDB

Answer

Amazon RDS for PostgreSQL

Question 10

A database administrator is troubleshooting an Amazon RDS for PostgreSQL DB instance that is experiencing high CPU utilization. The administrator runs the following query to find the current running queries:

SELECT pid, now() - pg_stat_activity.query_start AS duration, query, state
FROM pg_stat_activity
WHERE state = 'active';

The output shows a high number of queries with a state of 'active' and durations exceeding several minutes. What should the administrator do FIRST to reduce CPU utilization?

Accepted Answer

Use pg_terminate_backend to terminate the long-running queries.. The immediate cause of high CPU utilization is the long-running active queries consuming resources. Using pg_terminate_backend to terminate these queries will quickly free up CPU cycles, providing immediate relief. This is the first troubleshooting step before making configuration changes or scaling, as it directly addresses the symptom shown in the pg_stat_activity output.

Answer

Modify the max_connections parameter to limit concurrent sessions.

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Scale up the DB instance to a larger instance class.

Answer

Enable pg_stat_statements to collect query performance data.