Public clouds tend to be at least as reliable as the best-managed enterprise data centers. Most businesses can tolerate the minimal downtime that occurs in public clouds, which is outlined in a service-level agreement. But if your application requires ultra-high availability, you might want to host it outside of the public cloud.

Creating fallback or automated failover setups are more expensive to host in the public cloud than they are on premises. You can configure automated failover in the public cloud. But, if you want failover to happen instantly, you would need to pay for double the number of hosting resources. This gets pricey when you’re paying by the minute or the second to run virtual servers, as you would in the public cloud.