One zone vs two zones
Two servers in one zone fail together when the zone fails. Servers in two zones keep working when one zone is lost. At 1,200 orders/s, a zone A failure at 0:40 leaves 26.7 percent availability with both servers in zone A. With one server in each zone, availability is 99.4 percent for 4 USD/mo more.
Two rows · 3 of 3 replicas up · load served
Case 1
1,200 orders/s. Zone A fails at 0:40 and stays down. The balancer and the managed database span both zones. Availability must stay above 97.5 percent and p99 below 150 ms.
| Measure | Goal | Both servers in zone A | One server in each zone |
|---|---|---|---|
| Availability | at least 97.5% | 26.7% Fail | 99.368% Pass |
| p99 latency | under 150 ms | 30 ms Pass | 34 ms Pass |
| Monthly cost | 44 USD/mo | 48 USD/mo | |
| Error rate | 73.3% | 0.6% |