Which approach will meet these requirements?
Use Amazon EBS and configure the application AMI to use a snapshot of the same EBS instance on boot.
Use Amazon S3 and rearchitect the application so all uploads are placed in S3.
Use instance storage and share it between instances launched from the same Amazon Machine Image (AMI).
Use Amazon EBS and file synchronization software to achieve eventual consistency among the Auto Scaling group.
Explanations:
Amazon EBS volumes are tied to a specific instance and cannot be directly shared between instances in an Auto Scaling group. Using EBS snapshots for boot purposes does not provide a shared storage solution for file uploads.
Amazon S3 is a scalable, durable, and globally accessible object storage service. By rearchitecting the application to upload files to S3, all instances in the Auto Scaling group can access the same files immediately.
Instance storage is ephemeral and cannot be shared across multiple instances. It is also not persistent when instances are terminated or replaced in an Auto Scaling group.
Using Amazon EBS with file synchronization software introduces complexity and delay. EBS volumes are not designed to be shared across multiple instances, and synchronization would not provide real-time consistency, which is required in this case.
I sort that the answer is:
Use Amazon S3 and rearchitect the application so all uploads are placed in S3.