Well, OP, your requirements section is seriously lacking. You need "s3", but only local, non horizontally scalable?

You failed to answer why you even need s3... Why not a filesystem? Full stop. The entire point of s3 is distributed.

People write applications that work with the S3 API but may want to host their own storage for a variety of reasons. Personally I make use of S3-compatible services for pre-signed url access to data on disks I own. The distributed aspect is only one reason why someone might want an S3-like service.