The added support for FIX is interesting. As far as I can tell it's just TCP-level load balancing, is that right? HAProxy doesn't have the ability to, say, distribute each incoming order to a different backend server?
[1] https://www.haproxy.com/blog/haproxy-enterprise-2-3-and-hapr...
use_backend fix_servers_a if { var(txn.sendercompid) -m str firmA }
default_backend fix_servers_b
Then "fix_servers_a" could be defined as a round-robin backend.