Explanation

Amazon DynamoDB is a fully managed NoSQL database service that provides fast and predictable performance with seamless scalability. It's a key-value and document database that delivers single-digit millisecond performance at any scale.

Amazon ElastiCache is a fully managed in-memory data store and cache service that supports Redis and Memcached. While primarily used for caching, Redis (one of the engines supported by ElastiCache) is a NoSQL database that supports various data structures like strings, hashes, lists, sets, and more.

Why the other options are incorrect:

• Amazon Redshift: A fully managed data warehouse service designed for online analytical processing (OLAP), not a NoSQL database
• Amazon Aurora: A relational database service compatible with MySQL and PostgreSQL, not a NoSQL database
• Amazon RDS for MySQL: A managed relational database service for MySQL, which is a SQL database, not NoSQL

NoSQL databases are characterized by their non-relational data models and include document databases, key-value stores, wide-column stores, and graph databases.