Which solution will meet these requirements?

Explanations:

A partition placement group is designed for workloads that require spreading instances across different partitions to ensure high availability. It is not optimized for low-latency communication, which is a requirement here.

A compute optimized EC2 instance is not ideal for memory-intensive applications such as in-memory databases. In addition, a partition placement group would not address the low-latency requirement effectively.

A cluster placement group is designed for high-performance computing and low-latency networking within a group of EC2 instances. It ensures that instances are placed physically close together in the same availability zone, reducing network latency.

A spread placement group spreads instances across multiple physical servers to increase fault tolerance, but it does not minimize networking latency. This option is better suited for high-availability scenarios, not low-latency performance.