It says greater than 5 nines, and it's usually much greater - in usual times, these core services are usually at six or seven nines as measured client side. But

It says greater than 5 nines, and it's usually much greater - in usual times, these core services are usually at six or seven nines as measured client side. But it doesn't take long at three nines to destroy your five nine SLA. The other portion is client side retry logic. It's incredibly easy for developers to mark a lookup with a retry policy and timer, and one of the reasons that that latency is so low is so that even if there's a timeout, the pageview can succeed. The application code doesn't see the error at all if the retry is successful, it just takes longer. The retry code is very good and it's already known at the first rpc call where the retry should go - the connection pool maintains connections to multiple independent servers.