Even though we build applications like the old days, ISV’s have adopted the SaaS (Software as a Service) model and moved ahead from the traditional approach to offer their applications. Even though SaaS is maintained on the cloud and not hosted on-prem, there is a factor of SaaS that one should consider. With SaaS managing single and multiple tenants is possible. Each tenant (a user of your SaaS) has unique configuration model that is specific to them. This can be categorized as a single tenant architecture, and multi-tenant architecture.
The difference between these architectures are simple.
Imagine a single tenant model as your “house”, only your family members (users in your company) have access to your property. In technical aspects, your tenant has their own copy of the application with their own DB, and no data is integrated with other customers. The reason behind it is that there is only one system hosted in a particular cloud instance. The management portal can have its own URL, and can have unique branding/labeling specific to that tenant. Each tenant can also have their specific email servers.
Whereas a multi-tenant model is similar to a building where each tenant has access to only their part of the building, while few amenities and services are shared. With multi-tenant, multiple customers’ data co-exist in the same cloud instance on the same shared instance of the application. Here, the data is separated logically and secured, but no modifications or customizations may be made to the shared underlying structure. If you want to have multiple tenants with their label, respective URL and email servers, the best practice is to use the default tenancy model. Then you can create separate tenants for the Company A and Company B. Each tenant can have a unique branding, URL, identity store excepting a common email server.
When you consider which tenancy model is the best fit for your customers, the answers lies with your Business Analyst, and not by the fact that single tenancy has a superior security than multi-tenancy model.