DBS-C01 Workload-Specific Database Design Practice Test 6 — 15 Questions

Question 1

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?

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

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.

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Amazon DynamoDB

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Amazon RDS for MySQL

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Amazon Redshift

Question 2

A startup is building a real-time leaderboard for a gaming application. The data is highly dynamic with frequent updates and requires single-digit millisecond latency. Which database 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 real-time leaderboards with high-frequency updates. Its DAX (DynamoDB Accelerator) caching layer can further reduce read latency to microseconds, while its auto-scaling and on-demand capacity modes handle the highly dynamic workload without downtime.

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Amazon Neptune

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Amazon Redshift

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Amazon RDS for PostgreSQL

Question 3

A company needs to migrate an on-premises Oracle database to AWS with minimal changes to the application code. The application uses complex stored procedures and has high availability requirements. Which database service should be used?

Accepted Answer

Amazon RDS for Oracle. Amazon RDS for Oracle is the correct choice because it provides native Oracle compatibility, supporting complex stored procedures, PL/SQL, and existing application code with minimal changes. It also offers Multi-AZ deployments for high availability, meeting the requirement without requiring a complete rewrite.

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Amazon DynamoDB

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Amazon Redshift

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Amazon Aurora PostgreSQL

Question 4

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.

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Amazon QLDB

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Amazon ElastiCache for Redis

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Amazon RDS for MySQL

Question 5

A company is designing a multi-region active-active application that requires low-latency reads and writes across regions. The database must support conflict resolution. Which database should be used?

Accepted Answer

Amazon DynamoDB Global Tables. Amazon DynamoDB Global Tables is the correct choice because it provides a fully managed, multi-region, multi-active database that replicates data across regions with eventual consistency, supporting low-latency reads and writes. It includes built-in conflict resolution using a last-writer-wins (LWW) mechanism based on timestamps, which meets the requirement for conflict resolution in an active-active architecture.

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Amazon RDS Multi-AZ

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Amazon Redshift

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Amazon Aurora Global Database

Question 6

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

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Amazon Redshift

Question 7

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 8

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 9

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 10

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 11

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 12

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 13

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. 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 14

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 15

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'. 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