Amazon DynamoDB is a fully managed NoSQL database service that provides fast and predictable performance with seamless scalability and is designed to handle large amounts of data with consistent, single-digit millisecond latency which makes it suitable for applications that need high-performance data retrieval. On the other hand, Amazon RDS is primarily used for relational database use cases with SQL querying needs, whereas Amazon Redshift is a data warehouse solution optimized for complex querying over large datasets, and Amazon Neptune is a graph database service that is used for applications working with highly connected data.