It's $9/mo for 100 MB of ElastiCache Serverless which is HA.

It's $15/mo for 2x cache.t4g.micro nodes for ElastiCache Valkey with multi-az HA and a 1-year commitment. This gives you about 400 MB.

It very much depends on your use case though if you need multiple regions then I think DynamoDB might be better.

I prefer Redis over DynamoDB usually because it's a widely supported standard.

> It's $9/mo for 100 MB of ElastiCache Serverless which is HA.

You need to be more specific with your scenario. Having to cache 100MB of anything is hardly a scenario that involves introducing a memory cache service such as Redis. This is well within the territory of just storing data in a dictionary. Whatever is driving the requirement for Redis in your scenario, performance and memory clearly isn't it.