[jolux]

You successfully nerdsniped me and I'm having a lot of trouble finding discussion of the formal implications of what they call "strong consistency" here, other than reading that they did in fact formally verify it to some extent. The best that I could find is this other HN thread where people claim it is causally consistent in a discussion about a Deep Dive (frustratingly shallow, as it happens): https://news.ycombinator.com/item?id=26968627

[anonymousDan]

I have never heard strong consistency used to describe such a weak guarantee before - i.e. it's marketing bs. Usually strong consistency refers to linearizability (or at the least sequential consistency). The diagram a few pages in to this paper gives a nice overview: https://arxiv.org/abs/1512.00168

[jolux]

Yes I actually read that paper while I was digging around but it didn’t seem to help in this case because Amazon don’t specify whether reads made after a concurrent write is made are guaranteed to return the same value as each other. If they are I think the system would be linearizable, yes? Either way they don’t say linearizable anywhere and they describe it specifically as “read-after-write” so I think it would be wrong to assume linearizability. What’s missing from this model for linearizability? S3 doesn’t have transactions after all.

[andreareina]

Isn't this definition CAP consistency?

[anonymousDan]

CAP is defined wrt linearizability yes.