Amazon’s S3 outage yesterday brought down a large part of the internet, leaving thousands of companies and their customers stranded. While the outage itself only lasted about four hours, the effects were felt for much longer, and it highlighted how reliable the public cloud truly is.

One of the hardest things about cloud adoption for CIOs is dealing with the sense of losing control. For many CIOs, this came to light yesterday in AWS’ outage. That sense of loss of control weighed heavy on many executives and IT staff as they watched their websites and applications stop working, frustrating their entire customer base.

The promise of the public cloud is that it’s more affordable, and highly available. But the outage yesterday provided a reality check: If you’re going to use a high scale public cloud, you need to rewrite your application so that it can run in multiple regions. Few companies do this, thinking that the cloud is already resilient. It’s not.

And to seize control of your costs, you need to write your application so that it’s super efficient. In fact, Snapchat just reported that their cloud bill will exceed their revenue if they don’t find an alternative to their AWS architecture. Your developers need to know how much I/O, disk, CPU, RAM and other resources their code uses. This is the way code was developed for mainframes decades ago. Lots of attention was paid to the “efficiency” of an application.

But it is possible to use cloud services and still seize control of your outcomes. A full-service cloud provider has cost controls and resiliency built in to the architecture so you don’t have to rewrite your application. Online Tech offers protection against hardware failure built right into the infrastructure, and we offer the capability for an application to easily switch over to a different region, using Disaster Recovery as a Service. We have the data replication you need baked into the system at a fixed cost—meaning you don’t lose control of your costs, or your uptime.

The public cloud is a fantastic tool when used the right way, but if you’re not careful, you will soon find you’ve lost control of your business when the next outage happens.