A company is deploying a distributed in-memory database on a fleet of Amazon EC2 instances. The fleet consists of a primary node and eight worker nodes. The primary node is responsible for…

A partition placement group spreads instances across different logical partitions to reduce correlated failures, which does not prioritize the lowest possible networking latency between all nodes as effectively as a cluster placement group.

Compute-optimized EC2 instances are not the most suitable choice for an in-memory database, which primarily requires high memory capacity. A partition placement group also doesn't prioritize lowest latency.

A cluster placement group packs instances closely together within a single Availability Zone, optimizing for low network latency and high network throughput between them. This configuration, combined with memory-optimized EC2 instances (e.g., R-series) suitable for in-memory databases, provides the best performance for inter-node communication critical for distributed in-memory databases and data replication.

A spread placement group places instances on distinct underlying hardware to minimize correlated failures, rather than optimizing for low network latency between instances, and compute-optimized instances are unsuitable for an in-memory database.