AWS Certified Solutions Architect – Professional — Question 917

A company collects a steady stream of 10 million data records from 100,000 sources each day. These records are written to an Amazon RDS MySQL DB. A query must produce the daily average of a data source over the past 30 days. There are twice as many reads as writes. Queries to the collected data are for one source
ID at a time.
How can the Solutions Architect improve the reliability and cost effectiveness of this solution?

Answer options

• A. Use Amazon Aurora with MySQL in a Multi-AZ mode. Use four additional read replicas.
• B. Use Amazon DynamoDB with the source ID as the partition key and the timestamp as the sort key. Use a Time to Live (TTL) to delete data after 30 days.
• C. Use Amazon DynamoDB with the source ID as the partition key. Use a different table each day.
• D. Ingest data into Amazon Kinesis using a retention period of 30 days. Use AWS Lambda to write data records to Amazon ElastiCache for read access.

Correct answer: B

Explanation

Amazon DynamoDB is highly scalable and cost-effective for key-value lookups, making it ideal for querying specific source IDs with a partition key and timestamp sort key. Using Time to Live (TTL) automatically manages the deletion of data older than 30 days without incurring additional write costs, optimizing storage and cost efficiency. Other options, like Amazon Aurora with multiple replicas or daily DynamoDB tables, introduce unnecessary complexity and higher operational costs.