Just-in-time infrastructure
As you just saw, when deploying in the cloud, you only pay for the resources you provision. Most cloud companies use this to their advantage to scale their infrastructure up or down as the traffic to their sites changes.
This ability to add or remove new servers and services in no time and on demand is one of the main differentiators of an effective cloud infrastructure. In the example that follows, we can see the amount of traffic hitting Amazon.com during the month of November. Thanks to Black Friday and Cyber Monday, the traffic triples at the end of the month:
If the company was hosting their service in an old-fashioned way, they would need to have enough servers provisioned to handle this traffic such that only 24% of their infrastructure was used on average during the month:
However, thanks to being able to scale dynamically, they are able to provide only what they really need and dynamically absorb the spikes in traffic that Black Friday and Cyber Monday trigger:
Here at Medium, you also see, on a very regular basis, the benefits of having fast auto-scaling capabilities. Very often, stories become viral and the amount of traffic going on Medium drastically changes. On January 21, 2015, to our surprise, the White House posted a transcript of the State of the Union Address minutes before President Obama started his speech:
As you can see in the following graph, thanks to being in the cloud and having auto-scaling capabilities, our platform was able to absorb five times the instant spike of traffic that the announcement caused by doubling the number of servers our front service used. Later, as the traffic started to drain naturally, we automatically removed some hosts from our fleet:
