Which service will meet the requirements for storing the session information in the MOST cost-effective way?

Explanations:

Amazon ElastiCache with Memcached is primarily designed for caching and does not support persistence of session data. If the cache is lost, session data will be lost as well, making it unsuitable for storing session information reliably.

Amazon S3 is an object storage service optimized for durability and availability rather than low-latency access. It is not designed for storing session information that requires quick read and write access, making it less suitable for this use case.

Amazon RDS MySQL is a relational database service that can provide durability and availability, but it may not be as cost-effective for session management due to overhead, and it could introduce latency compared to in-memory solutions. It also requires more management in terms of scaling and availability.

Amazon ElastiCache with the Redis engine provides in-memory data storage with low latency, high availability, and support for data persistence. Redis also has features such as automatic scaling and replication, making it a cost-effective and suitable choice for storing session information in a highly available and scalable manner.