The only time it makes sense to use EFS is when you want to have multiple servers with concurrent, consistent read+write access to a shared network filesystem. That's an expensive architectural decision that's best avoided if at all possible, to be sure; personally, I would prefer not to build a service that takes a dependency on EFS. But comparing it to "just" using an SSD with some sort of replication is kind of silly.

https://aws.amazon.com/efs/when-to-choose-efs/

If thought-experimenting a cheaper alternative to EFS, remember to include:

- Continuous availability to the filesystem without data loss if you lose a data center

- Close-to-open consistency semantics https://docs.aws.amazon.com/efs/latest/ug/how-it-works.html#...