Google recommends using at least 3 cloud servers in the production environment for redundancy. That is why stape set up 3 servers for Pro plan users and 5 cloud servers for Business plan users. This way,  we ensure your tagging server infrastructure is stable and scalable. 

The multi-cloud server setup is required for redundancy and stability of the sGTM container. Please note that 3 cloud servers do not mean you can use the Pro container for 3 websites. One container should be used for one site (unless you need a multi-domain feature).