hej @jfowler
short answers to your questions
1. Multiple web frontend use case?
Having multiple Servers serving the API / Web become more important when having a higher count of users - but it is not really needed, but it does not harm.
2. Processing
- global inputs have the advantage that any node is able to take work on that input
- you need to balance the traffic yourself between all nodes, no distribution of work
- you need to decide yourself what way of balancing you choose - once a message reaches one GL server it will be processed and stored according to your configuration in ES.