Single Tenant is a single instance of the software and supporting structure serving a single customer. With a single tenant, each customer has their own dependent database and instance of the software. Essentially, there is no sharing across tenants. This is rare and is generally reserved for very large enterprise level clients – typically 15,000 users and above.
Multi-Tenant means that a single instance of the software with it’s supporting infrastructure serves multiple customers. Each customer shares the software application and also shares a single database. Each tenant’s data is isolated and remains invisible to other tenants. This is the typical deployment for customers sub 15,000 for a “UCaaS / CCaaS”.