Which AWS service will meet this requirement?

Explanations:

Amazon DynamoDB is a fully managed NoSQL database service designed to handle high-scale workloads, capable of processing millions of requests per second with low latency and automatic scaling features.

AWS Cloud9 is a cloud-based integrated development environment (IDE) that allows developers to write, run, and debug code, but it is not a data store and does not meet the requirement for handling database queries.

Amazon ElastiCache for Memcached is an in-memory caching service that improves application performance by storing frequently accessed data, but it is not a persistent data store suitable for scaling millions of queries per second as a primary database solution.

Amazon Neptune is a graph database service that is optimized for connected data and provides high availability and performance, but it is not specifically designed for the massive scalability needed to handle millions of database queries per second like DynamoDB.