This means Cellar does not qualify this year for the "five nines" category of "highly available", and only qualifies as "three nines". (It's only available 99.9% of the time, not 99.999% of the time.) In recent years, the regular failure of platforms like Amazon AWS has meant that even huge sites have had a hard time managing to reach that goal. So we're doing OK.
No single-point-of-failure solution is ever really highly available. To qualify we would need failover with at least one other server in a load-balancing platform.