Mulesoft's Anypoint CloudHub is the iPaaS that provides auto-scaling Mulesoft runtimes and other associated services for the entire infrastructure. CloudHub offers HA by default when any integration application is deployed on to the runtimes of Anypoint CloudHub. The underlying AWS services provide the HA based on the number of workers you assign to the application/integration.
One of the crucial components that helps in achieving this is the "load balancer." As an organization, you may use the public load balancer that is available to any of the application deployed on CloudHub runtimes. This, however, comes with the default CloudHub domain, "<your-vpc-region>.cloudhub.io." The other approach — a more appropriate and most used one — is to have a custom domain name for your organization application. And this is logical as well. If you have services and applications that are specific to your organization, you will want to have a custom domain name and not use the default CloudHub's domain. The other important features this would provide are the abilities to configure your own custom routing rules, TLS certificates, and firewall rules for your own custom load balancer, amongst other things.