The idea that Amazon S3 is really an 'Amazon Cloud Filesystem' is a bit of a fiction - it isn't a file system and it can't stand in for one. S3 implements a completely different arrangement and its primitives are only partly compatible with the Unix file API. It has fewer functions and can't do some tasks, such as overwriting files partially. This means that filesystem software, especially databases, can't be ported to Amazon S3.

While S3 is undoubtedly a feat of engineering, its feature set is falling behind its competitors. S3 doesn't have a compare-and-swap operation, something every other competitor has, and it also lacks multi-region buckets and object appends. Engineers wanting any of these features have to either abandon S3 or build around these gaps.

S3, Amazon's object storage service, is missing features like compare-and-swap (CAS), multi-region buckets, and object appends. S3 Express One Zone, S3's faster alternative, lacks many standard S3 features and has high storage costs. As S3 continues to not have these modern features, developers will have to either build workarounds or move on to an S3 alternative.