The correct choice is Memory Optimized instances because they provide the large RAM capacity and high memory bandwidth needed when session state and real time rankings must reside in memory to meet sub millisecond response requirements.

Memory Optimized instances are built for in memory caches and databases and they deliver the high memory footprint and bandwidth required to keep the working set in RAM for ultra low latency access. Select an instance size in the family that balances vCPU and network performance for your concurrency and consider instances with enhanced networking for consistent latency.

Compute Optimized instances focus on vCPU performance for compute bound workloads and they do not prioritize large memory capacity so they are not ideal for an in memory session store.

Accelerated Computing instances provide GPUs or FPGAs for specialized acceleration such as machine learning or graphics tasks and they are not intended for general purpose in memory caching needs.

Storage Optimized instances are tuned for high throughput and low latency access to local storage and they optimize disk I O rather than offering the large RAM footprint required to keep session state fully in memory.

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