Asif Fraz wrote:1. If your system is to be used by a limited number of clients, is it a good idea to put your system behind firewalls and allow its access via private VPN? In this way you will keep public access out of the way.
2. If you put vpn in place will it effect response time significantly?[
Having a firewall between the public internet and your app servers will increase your security given a proper firewall configuration.
A common use of VPN is for employees to access company network and resources (as if they were at their desk computer).
Firewall and VPN are 2 separate things and for different purposes.
With VPN in place, if you are concerned with user overload maxing your servers' resources, then load balancing or clustering is more appropriate.
Hope this helps.