DBS-C01 Workload-Specific Database Design Practice Test 5 — 15 Questions

Question 1

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.

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Amazon RDS for MySQL

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Amazon DynamoDB

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Amazon Redshift

Question 2

A company is running a MongoDB workload on-premises and wants to migrate to AWS with minimal operational overhead. The application uses MongoDB-specific features like aggregation pipelines. Which service is best?

Accepted Answer

Amazon DocumentDB. Amazon DocumentDB is the correct choice because it is a fully managed, MongoDB-compatible document database that supports MongoDB-specific features like aggregation pipelines, indexes, and queries. It minimizes operational overhead by handling hardware provisioning, patching, backups, and replication, making it ideal for migrating an on-premises MongoDB workload to AWS without significant application changes.

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Amazon DynamoDB

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Amazon RDS for PostgreSQL

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Amazon Elasticsearch Service

Question 3

A company needs to build a reporting dashboard that queries a large dataset stored in Amazon S3. The queries are complex and require full SQL support. Which service should be used?

Accepted Answer

Amazon Athena. Amazon Athena is the correct choice because it is a serverless, interactive query service that allows you to analyze data directly in Amazon S3 using standard SQL. It supports complex queries, including joins, window functions, and CTEs, and requires no infrastructure management, making it ideal for ad-hoc reporting on large datasets in S3.

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Amazon Redshift Spectrum

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Amazon RDS

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Amazon DynamoDB

Question 4

A company is designing a social media application that requires storing user relationships (follows) and making graph queries like 'mutual friends.' Which database is most suitable?

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 Gremlin or SPARQL to efficiently traverse relationships like 'mutual friends' in a social media application, making it the ideal choice for graph queries.

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Amazon ElastiCache for Redis

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Amazon DynamoDB

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Amazon RDS for MySQL

Question 5

Which TWO of the following are best practices for designing a DynamoDB table for high traffic? (Choose 2)

Accepted Answer

Use global secondary indexes for alternate access patterns. Global secondary indexes (GSIs) allow you to define alternate partition and sort keys to support different query patterns without duplicating data. This is a best practice for high-traffic workloads because it enables efficient access to data using multiple access patterns while maintaining a single base table, reducing the need for expensive scans or application-level joins.

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Store large items to reduce the number of items

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Use normalized tables and perform joins in application

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Always use strongly consistent reads for best performance

Question 6

Which THREE factors should be considered when choosing between Amazon RDS Multi-AZ and Amazon Aurora for high availability? (Choose 3)

Accepted Answer

Aurora provides faster failover (typically under 30 seconds). Aurora's distributed storage architecture enables failover in under 30 seconds typically, because the storage layer is shared across all instances in the cluster. When the primary instance fails, Aurora simply promotes one of the existing read replicas to primary, without needing to remap storage volumes. This is significantly faster than RDS Multi-AZ, which requires a DNS change and a synchronous block-level replication failover that can take 60-120 seconds.

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RDS Multi-AZ provides automatic scaling of storage

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RDS Multi-AZ supports encryption at rest

Question 7

Which TWO are valid use cases for Amazon ElastiCache for Redis? (Choose 2)

Accepted Answer

Session management for web applications. Amazon ElastiCache for Redis is an in-memory data store ideal for session management because it provides sub-millisecond latency for storing and retrieving session tokens, supports TTL-based key expiration to automatically clean up stale sessions, and offers atomic operations like SETEX for safe session creation. This makes it a perfect fit for stateless web applications that need to offload session state from the application server.

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Storing graph data with relationships

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Running complex analytical queries on large datasets

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Persistent storage of relational data

Question 8

A database administrator runs the above command. The database is currently in a healthy state. Which statement is true about this database?

Accepted Answer

The database is deployed in a Multi-AZ configuration. Option C is correct because the command output shows the database is in the 'creating' state with 'multi-az': True. This explicitly indicates that the database is being deployed in a Multi-AZ configuration, which provides high availability by synchronously replicating data to a standby instance in a different Availability Zone.

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The database engine is Amazon Aurora

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The database uses a burstable instance class

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The database has a read replica in another region

Question 9

An IAM policy is attached to a user to restrict access to a DynamoDB table. What does this policy allow the user to do?

Accepted Answer

Read and write items only where the partition key equals 'customer_123'. The IAM policy uses a condition key `dynamodb:LeadingKeys` with a condition operator `ForAllValues:StringEquals` to restrict access to items where the partition key equals 'customer_123'. This allows the user to perform read and write operations only on items matching that specific partition key value, enforcing fine-grained access control at the item level.

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Read and write any item in the Orders table

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Scan the entire Orders table

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Perform all DynamoDB actions on the Orders table

Question 10

A developer sees the above key schema for the ProductCatalog table. Which query will be most efficient for retrieving a single item?

Accepted Answer

GetItem with ProductId = '123' and Category = 'Books'. Option D is correct because the ProductCatalog table's primary key is a composite key of Category (partition key) and ProductId (sort key). A GetItem operation with both the partition key and sort key provides the most efficient direct access to a single item, as it uses the primary key to retrieve the item with exactly one read operation, without any filtering or scanning.

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Query with Category = 'Books'

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GetItem with ProductId = '123'

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Scan the table and filter by ProductId

Question 11

A company is designing a database for a real-time bidding system that requires sub-millisecond read and write latency for ad impressions. The workload is heavily write-intensive with occasional reads by campaign IDs. Which AWS database service is most suitable?

Accepted Answer

Amazon DynamoDB with DAX. Amazon DynamoDB with DAX is the most suitable choice because DynamoDB provides single-digit millisecond latency for read and write operations at any scale, and DAX (DynamoDB Accelerator) is an in-memory cache that reduces read latency to microseconds for frequently accessed items. This combination meets the sub-millisecond read and write latency requirements for a heavily write-intensive real-time bidding system, while supporting occasional reads by campaign IDs via efficient query patterns.

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Amazon ElastiCache for Redis

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Amazon DocumentDB

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Amazon Aurora MySQL

Question 12

A gaming company uses Amazon RDS for PostgreSQL to store player profiles and game state. They report slow queries during peak hours. The DB instance is a db.r5.2xlarge with 500 GB gp2 storage. Which design change would MOST improve read performance for the most frequently accessed player profiles?

Accepted Answer

Add a read replica in the same AZ. Adding a read replica in the same Availability Zone (AZ) offloads read traffic from the primary RDS for PostgreSQL instance, directly improving read performance for frequently accessed player profiles during peak hours. Read replicas asynchronously replicate data using PostgreSQL's streaming replication and can serve SELECT queries without impacting the primary instance's write workload or connection limits.

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Implement application-level sharding by player ID

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Increase provisioned IOPS on the existing volume

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Upgrade to a db.r5.4xlarge instance

Question 13

A financial services company needs a relational database with high availability and automatic failover across three Availability Zones in us-east-1. The workload consists of OLTP transactions with occasional analytic queries. Which database solution meets these requirements?

Accepted Answer

Amazon Aurora MySQL with Multi-AZ deployment across 3 AZs. Amazon Aurora MySQL with Multi-AZ deployment across 3 AZs meets the requirements because Aurora automatically replicates your data six ways across three Availability Zones, with a primary DB instance in one AZ and two read replicas in the other two AZs. In the event of a failure, Aurora automatically fails over to a read replica in under 30 seconds without data loss, providing high availability and automatic failover across three AZs. Aurora also supports both OLTP transactions and can handle occasional analytic queries via Aurora Replicas or Aurora Global Database for read scaling.

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Amazon RDS for MySQL with Multi-AZ (2 AZs)

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Amazon DynamoDB global tables

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Amazon Redshift with cross-region snapshots

Question 14

A company is migrating an on-premises MongoDB database to AWS. The database stores JSON documents for a content management system. The workload requires read-after-write consistency and automatic scaling. Which AWS database service is MOST appropriate?

Accepted Answer

Amazon DocumentDB. Amazon DocumentDB is the most appropriate choice because it is a fully managed, MongoDB-compatible document database that natively stores JSON documents, supports read-after-write consistency via its default session consistency model, and provides automatic scaling of storage (up to 64 TB) and compute resources. It directly replaces on-premises MongoDB workloads without requiring schema changes or application rewrites, making it ideal for a content management system.

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Amazon ElastiCache for Redis

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Amazon DynamoDB

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Amazon RDS for PostgreSQL

Question 15

A company runs a global e-commerce platform with a relational database. They need to reduce read latency for users in Europe and Asia. The primary database is in us-west-2. Which solution provides the LOWEST read latency for global users while maintaining data consistency?

Accepted Answer

Use Amazon Aurora Global Database with reader instances in Europe and Asia. Amazon Aurora Global Database is designed for low-latency global reads by replicating data to up to five secondary regions with dedicated reader instances. It uses storage-based replication that typically adds less than one second of lag, ensuring strong consistency while providing local read access for users in Europe and Asia. This architecture directly addresses the requirement for the lowest read latency without compromising data consistency.

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Deploy Amazon ElastiCache clusters in each region and cache database queries

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Migrate to Amazon DynamoDB global tables

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Configure Amazon RDS cross-region read replicas