Amazon CloudSearch is a search engine as a service from Amazon that allows users to store their documents on CloudSearch, provides indexing on those documents and provides a search engine kind of functionality with faceted search options. CloudSearch scales as the number of documents increases with time. Using CloudSearch is quite easy—you just need to create one CloudSearch domain where you need to specify the attributes of each document you are going to store. Appropriate data types are provided in order to improve the search functionality.

To store a document in CloudSearch, you have to generate your data in SDF format. SDF is nothing but Search Document Format, which is a JSON document that holds the metadata about the document with actual data. Once the document is stored on CloudSearch, you can simply search for the document using the CloudSearch console or search API given by Amazon.

There might be a use case where you want to use DynamoDB as your storage...