Comment by mjb
2 days ago
That’s a fair point. To be fair to the academic definitions, “eventually consistent” is a quiescent state in most definitions, and there are more specific ones (like “bounded staleness”, or “monotonic prefix”) that are meaningful to clients of the system.
But I agree with you in general - the dynamic nature of systems means, in my mind, that you need to use client-side guarantees, rather than state guarantees, to reason about this stuff in general. State guarantees are nicer to prove and work with formally (see Adya, for example) while client side guarantees are trickier and feel less fulfilling formally (see Crooks et al “Seeing is Believing”, or Herlihy and Wing).
I have no beef with the academic, careful definitions, although I dislike the practice where academics redefine colloquial terms more formally. That actually causes more, not less confusion. I was talking about the colloquial use of the term.
If I search for "eventual consistency", the AI tells me that one of the cons for using eventual consistency is: "Temporary inconsistencies: Clients may read stale or out-of-date data until synchronization is complete."
I see time and time again in actual companies that have "modern" business systems based on microservices that developers can state the same idea but have never actually paused to think that you something is needed to do the "synchronization". Then they build web UIs that just ignore the fact, causing application to become flaky.