The main difference between public cloud and private cloud is where it is hosted and who is responsible for managing it. Public cloud uses shared infrastructure, while private clouds use your organization’s own dedicated infrastructure. Other common cloud models include hybrid cloud, which combines public and private clouds, and multicloud, where customers employ cloud services spanning multiple public clouds.

Public cloud platforms, such as Google Cloud, pool resources in distributed data centers around the world that multiple companies and users can access from the internet. Rather than an in-house team, the public cloud providers are responsible for managing and maintaining the underlying infrastructure. As a result, leveraging public cloud services reduces IT operational costs and frees up time for teams to focus on valuable work that directly benefits the business.

A common public cloud example is to think of it as similar to renting an apartment: 

• You pay rent for a single unit
• The building manager handles the maintenance
• You share the overall space with other tenants, with security around your own belongings

Private cloud is more like owning a house, where you have your own personal space that belongs to you, but you’re also personally responsible for the overall care and upkeep. However, there are cases where a business may choose a private cloud to fulfill certain requirements, such as industry or region-specific compliance and data sovereignty needs.   

One key caveat to this analogy is that property can’t elastically scale whereas cloud resources can. Unlike renting an apartment that is a fixed size, you can easily scale up a “public cloud” apartment into a mansion, if you wanted to throw a party for a million people, and scale back down to an apartment the next day. 

The same goes for a house you own: it can only be extended through renovation. Private cloud requires purchasing hardware to meet demand, as well as any licensing costs needed for software applications. Similarly, an on-premises IT stack can’t easily accommodate surges in traffic without staff having to purchase and install new resources (which might go unused until the next surge or decay into technical debt). 

Public cloud lets you automatically scale up your compute and storage resources along with the increased security and services you need.