Listing things is very common, so why would you outsource that to S3 when all your bookkeeping is elsewhere? It's not like you would ever rely on the POSIX API for that anyway, even for when your files actually are on a POSIX filesystem.
For sure, for maintenance tasks etc. it sounds quite useful. And good hygiene with prefixes sounds like a sane idea. But listing being a critical part of what "makes S3 useful"? That seems like an huge stretch that your points don't seem to address.
> It's not like you would ever rely on the POSIX API for that anyway, even for when your files actually are on a POSIX filesystem.
Because there is no POSIX api for this. Depending on your requirements and query patterns, you may not need a completely separate database that you need to keep in sync.
For sure, for maintenance tasks etc. it sounds quite useful. And good hygiene with prefixes sounds like a sane idea. But listing being a critical part of what "makes S3 useful"? That seems like an huge stretch that your points don't seem to address.