Thanks for the reply Pramod. I had this so was looking for answers to my persistence question. I have been directed to the load balancer set up for the ARS servers and there persistence is required, where it is not on the mid-tiers so I was looking for some clarification. I have answers to the mongodb cluster based on their FAQ (FAQ: Concurrency — MongoDB Manual 3.6 ).
For Smart IT you can use F5 LB, all Smart IT servers will be active/active, user load will be based on load balancing method used at LB level. For persistence type you can use cokie or source.