> There are some systems that claim to beat CAP but they typically have caveats and assurances that are required.
If by “caveats and assurances,” you mean “relax the definitions of CAP,” then yes. CAP, in its strict definition, has been formally proven [0].
> After-all, if you ack a write, and then that node blows up, how will it ever sync?
That’s just async replication.
0: https://www.comp.nus.edu.sg/~gilbert/pubs/BrewersConjecture-...
No disagreement. I was making space for a system like spanner whilst alluding to the fact it still needs to choose.