Cloud hosting is renting the computers, storage and network that an app or a website needs from a provider, instead of buying them. It is also called cloud infrastructure, or infrastructure as a service (IaaS). The provider owns the machines in its data centres and keeps them running. The customer rents a share of them over the internet, and pays only for what it uses. This is what cloud computing means.
Every app has a backend, the part that the user never sees. The backend stores the data, checks logins and runs the app's rules, such as working out the price of an order. It runs on servers. A server is a computer without a screen. It sits in a data centre and answers requests that other computers send it over the internet.
Take, for example, a five-person start-up in Pune that is building a food-ordering app. The team does not want to buy servers, or rent space in a data centre to keep them in. So it rents everything it needs, piece by piece.
First, it buys its web address, a .in name, from a company called a registrar. This is domain registration and DNS. DNS, the Domain Name System, turns the name into the numeric address of the team's server. The team also gets a certificate. The certificate shows the padlock in the browser, and lets the browser encrypt everything sent to the site. The page on public key infrastructure explains how certificates work.
Next, it rents a server from a developer cloud. The server is a virtual machine, a slice of a real server that behaves like a computer of its own. It is billed by the hour. The team also rents storage, paid for by the amount of data it holds, and a managed database. The provider installs, updates and backs up the database for the team.
The team's marketing website has only a few simple pages. So it sits on cheaper web hosting, where many small websites share one server and split its cost.
Then the team adds a content delivery network (CDN). A CDN has servers in many cities, and they keep copies of the app's images and pages. So a customer in Guwahati or Kochi receives them from a nearby server, and not from the team's server in Bengaluru. The CDN also blocks attack traffic before it reaches the team's server. It can even run small pieces of the app's code near the user. Running computing close to the user like this is called edge computing.
What does all this cost? In the first month, a small server, a database and some storage may cost the team a few thousand rupees. On a busy Friday night, the team can add servers for a few hours and pay only for those hours.
A few years later, the same company may have hundreds of servers across many cloud accounts. Nobody remembers which servers are still needed. A cloud management platform then lists everything the company rents, switches off what is idle, and checks the setup against the rules the company must follow.
The three biggest cloud providers, AWS, Microsoft Azure and Google Cloud, are called hyperscalers. Together they hold most of this market. This scene covers the providers and tools around them, which smaller teams often choose for their shorter menus and simpler prices.