What is the difference between public and private SaaS?

Public and private SaaS (Software as a Service) differ primarily in their deployment models, infrastructure ownership, and target audiences. Public SaaS refers to applications hosted and managed by a third-party provider on shared infrastructure, accessible to multiple customers over the internet. Examples include platforms like Salesforce or Slack, where users subscribe to a service without managing the underlying servers. Private SaaS, on the other hand, is deployed on dedicated infrastructure, often tailored for a single organization or a restricted group of users. This model is common in industries with strict compliance or security requirements, such as healthcare or finance, where data control is critical.

From a technical perspective, public SaaS relies on multi-tenant architecture, where resources like servers, databases, and storage are shared across customers. This approach reduces costs and simplifies scaling but introduces limitations in customization and data isolation. For instance, a developer using a public SaaS tool like GitHub Actions might have limited control over where workflows execute. Private SaaS, however, typically uses single-tenant infrastructure, allowing organizations to customize security policies, integrate with on-premises systems, or meet regulatory needs. A bank, for example, might deploy a private SaaS loan management system on its own servers to ensure compliance with data residency laws.

The choice between public and private SaaS depends on use-case requirements. Public SaaS suits startups or teams prioritizing rapid deployment, cost efficiency, and minimal maintenance. Developers can integrate APIs or pre-built services without managing infrastructure. Private SaaS is ideal for organizations needing full control over data governance, performance, or compliance. A government agency handling sensitive citizen data might opt for a private SaaS solution hosted in a sovereign cloud. While private SaaS offers greater flexibility, it requires significant upfront investment in infrastructure and ongoing maintenance, making it less accessible for smaller teams. Both models have trade-offs, and hybrid approaches (combining public and private) are increasingly common to balance scalability and control.