The most famous laptop sticker in history offers a humorously simplistic definition of cloud computing:

The “cloud” is nothing more than a collection of computers sitting in data centers around the world. You can rent these computers by the hour. Some are pre-configured to run higher-level services such as database management systems, DNS servers, authentication, load balancers, machine learning algorithms. These higher-level services tend to cost a little bit more.

However, while the cloud is nothing more than somebody else’s computer, “cloud computing” has changed how developers and system designers approach web development. Initially, the benefit is having “somebody else” care for physical handling and maintenance of the equipment (purchasing, shipping, installation, power, cooling, physical security, network connections). However, once you no longer own the equipment, you can rent precisely what you need, when you need it, for as long as you need it, and as much of it as you need.

The flexibility is extraordinary. AWS Lambda allows you to rent a computer for 100 milliseconds for $0.0000002083. ^[1]

The flexibility also brings about a mindset shift from thinking about computers as things that need to be individually managed, to the idea of a web application as a growing and shrinking pool of computing resources. Some servers will crash or be overloaded, but the system should adapt automatically and add or replace servers as needed.