What is the main use of Amazon ElastiCache?

The main use of Amazon ElastiCache is to provide in-memory caching services for applications. This service significantly improves the performance of web applications by allowing for faster data retrieval. When an application retrieves data from a database, there is often a delay due to the time it takes to execute queries and access the underlying storage system. By using ElastiCache, frequently accessed data can be stored in memory, allowing the application to fetch this data much more quickly.

This caching mechanism can dramatically reduce the load on databases and other backend resources, leading to improved response times and overall application performance. ElastiCache supports popular caching engines such as Redis and Memcached, which are widely used in the industry for efficient data caching scenarios.

The other options describe services that are not related to the function of ElastiCache. For instance, storing large datasets in a NoSQL database pertains to services like Amazon DynamoDB, while automatic backups and running machine learning models are functionalities associated with different AWS services.