Amazon DynamoDB is a key-value and document database that delivers single-digit millisecond performance at any scale. It is a fully managed, serverless database that does not require provisioning, patching, or backup. It offers built-in security, backup and restore, and in-memory caching3. Amazon RDS is a relational database service that makes it easy to set up, operate, and scale a relational database in the cloud. It provides cost-efficient and resizable capacity while automating time-consuming administration tasks such as hardware provisioning, database setup, patching, and backups. However, it is not a key-value NoSQL database, and it is not serverless, as it requires you to choose an instance type and size4. Amazon Aurora is a MySQL and PostgreSQL-compatible relational database built for the cloud, that combines the performance and availability of traditional enterprise databases with the simplicity and cost-effectiveness of open source databases. However, it is also not a key-value NoSQL database, and it is not serverless, as it requires you to choose an instance type and size. Amazon MemoryDB for Redis is a Redis-compatible, durable, in-memory database service that delivers ultra-fast performance and multi-AZ reliability for the most demanding applications. However, it is also not a key-value NoSQL database, and it is not serverless, as it requires you to choose a node type and size.