Theorems are all well and good, but ultimately the thing that matters is the experience of using the system "IRL" as the kids say. If spanner is up 99.99% of the time, and is consistent at all times, it is probably not going to be the weak link in your software chain.
(Fwiw their slo for multi-regional instances is 99.999%, although I have no idea what their measured performance is against that objective.)
(Fwiw their slo for multi-regional instances is 99.999%, although I have no idea what their measured performance is against that objective.)